- “Oh, Louis would give anything to be up there jammin' with the big boys....”
Early on in the story, Louis was meant to be so cowardly, phobic, and timid that even frogs can frighten him. Eventually, however, directors John Musker and Ron Clements changed the character into what is seen today.
Also, according to The Princess and the Frog's DVD commentary on the film, Louis was, at one point, meant to be a human with a passion for music. However, he was a terrible musician and eventually went to Dr. Facilier to gain the ability to play the trumpet through magic. Facilier gave him the ability, but turned him into a gator as well, leaving Louis stranded in the bayou trying to find a way to reverse the curse just before meeting Tiana and Naveen. The idea was soon dropped for being too complicated for the story.
Despite his size and ferocious appearance, Louis is a gentle giant with a heart of gold. He is very fond of his trumpet and his dream is to become a famous jazz singer who can perform in front of a human audience without scaring anyone. He believes the only way to do this is to become human himself, prompting the gator to join Tiana and Naveen to find Mama Odie. He is notable for having a few phobias, though they prove to be understandable. The most notable of which being his fear of guns and the hunters that wield them. Along with that, Louis has a great fear of "pricker brushes" and traps set throughout the bayous for gators, tying in with his fear of hunters.
Despite being generally known as a coward, Louis has still proven to be quite upbeat and lively a lot of times, specifically when he's in a good mood or has the urge to play his trumpet. He has also shown to have quite the knowledge about humans and their culture. With riverboats constantly making their way through the bayous of New Orleans, Louis has received the opportunity over the years to familiarize various jazz tunes, eventually becoming the masterful trumpet player he is. Aside from music, he also knows quite a lot about human food, which is also shown to be another love of his.
Louis is large, overweight, and taller than a grown man. He was animated by Eric Goldberg, who's known for his previous work on other famous characters such as Genie in Aladdin. Goldberg also won an Annie Award for his animation on the gator.
In earlier stages of the film, Louis' design was in the "cartoony" variety, as Goldberg states, and was seen with a pair of glasses; This echoes the original concept of Louis being a human turned into a gator by Dr. Facilier. When the story altered, Eric Goldberg used both the references of real-life alligators, and the consult of his fellow animators, to arrive at the final design of the gator. 
Louis first meets Tiana and Naveen when they are stranded in the bayou. The duo are terrified of Louis when they first see him, thinking he is about to eat them, but Louis reveals his friendly nature by recognising a jazz tune Naveen was playing on his ukulele. Louis tells Naveen of his dream to be a famous jazz player in New Orleans, but explains that his last attempt to play with humans ended with his audience panicking at the sight of an alligator. When Tiana and Naveen explain that they are actually humans turned into frogs by a voodoo witch doctor, Louis, knowing about voodoo, tells them about Mama Odie, the voodoo queen of the bayou who might be able to reverse the curse. At first, Louis is too scared to take them to the deepest, darkest part of the bayou where she lives because of the dangers there, but is convinced by Naveen that she could make Louis "smaller and less toothy," so that he can play music for humans without scaring them; Louis decides to ask Mama Odie to turn him human.
In excitement of the oncoming future, Louis, Tiana, and Naveen sing about what life would be like once they're human. During the journey, Louis learns of Tiana's dream to open a restaurant, and appears to be very excited about the idea, mostly because of his great love of food. However, after getting lost in the swamp, they meet a Cajun firefly called Ray, who helps guide them to Mama Odie's home. In the mix of their journey, the group encounters a trio of frog hunters, stunning. a fearful Louis, who jumps into a bush of thorns. After Tiana and Naveen manage to defeat the hunters, Louis' injuries force the journey to come to a slight hault, as Ray needs time to remove each thorn from Louis' body. As they rest, Louis bonds with his three new companions, and comes to support Tiana and Naveen as lovers. During the bonding, however, the gang is attached by a hoard of shadow demons, sent by Doctor Facilier, to kidnap Naveen. Louis, Tiana, and Ray chase after the frog prince, until a mysterious being arrives and defeats the shadowy creatures with ease. Louis looks upon in fear as the mysterious being is soon revealed to be the eccentric Mama Odie.
Mama Odie (who isn't as fearsome as Louis initially assumed) tells Tiana and Naveen to "dig a little deeper" to find what they need, as opposed to what they want, but also tells them that Naveen must kiss a princess to break the spell. Using her magic brew, Mama Odie locates one; Tiana's best friend, Charlotte La Bouff, who is a princess due to her father being crowned King of the Mardi Gras parade. Louis then asks to be human like his two friends, but she tells him to "dig a little deeper" as well.
The friends begin to head off, when Louis gets the idea to have them stowaway on a riverboat to get there quicker. However, Louis is immediately noticed by a jazz band who believe, like themselves, the gator is merely a man dressed in an animal costume, and they invite him to play with them in the parade. Louis is thrilled and immediately joins them. However, at the Mardi Gras parade, Louis notices Ray fleeing Dr. Facilier's Shadow Demons and stops playing, at which everyone realizes he's a real alligator. By the time Louis is able to catch up with Ray, he is too late. Louis finds the crushed body of Ray in St. Louis Cemetery and recovers him, rushing off to find Tiana and Naveen, the firefly not having much time before he departs from the world.
Because of Louis, Ray is able to see his friends one last time before peacefully passing away. Crushed, Louis immediately begins to tear up in sorrow. The heartbroken trio attend Ray's funeral to bid a final farewell. During a moment of silence, Louis and his friends look into the night sky and notice a star shining brightly beside Evangeline, which appears to be Ray finally reuniting with his beloved.
Everyone is overjoyed, and the friends head to Mama Odie for Tiana and Naveen's bayou wedding. After Tiana and Naveen are pronounced frog and wife, a kiss follows, turning the two back into human, as Tiana was now a princess through marriage. The bayou inhabitants celebrate the love and success, including Louis, who later helps Tiana buy her restaurant by growling intimidatingly at The Fenner Bros (who were the sellers of the building Tiana planned on buying for her dream restaurant), scaring them into handing over the keys to the building. Once Tiana's Palace opens, Louis is finally able to live out his dream of being a famous musician, becoming the leader of the Palace's exclusive band, the Firefly Five plus Lou, even though he is still an alligator.
Cameos and other appearances
In anticipation for the 82nd Academy Awards, Naveen made an appearance in an online "interview", accepting the film's nomination with pride, though an excitable Louis was quick to crash the session, beleiving they had already won the award.
The Grand Opening
As the opening of Tiana's restaurant is on the rise, things begin to run amuck for the princess and her employees. For Louis, his trumpet goes missing, forcing Tiana and Naveen to assist him in finding it, as he finds it impossible to perform without it. After seemingly endless searching, Louis sadly tells his friends he'd rather them focus on getting the restaurant together, telling them he'd be fine. However, just as the moment arrives, Tiana manages to recover the missing trumpet.
Tiana and her Furry Friend
Louis makes a brief appearance near the end of the book, where his appearance in the kitchen of Tiana's Palace frightens a wandering Stella, the dog of Charlotte La Bouff. Tiana and Naveen manages to calm the furry girl, just before she's able to harm Louis, who the royal couple revealed to be harmless.
A Hidden Gem
In this story, Naveen is on the hunt for swamp amber, as a gift for Tiana. After meeting up with Louis, the duo asks Mama Odie if she knew of the amber's whereabouts, but they were told they didn't need her assistance and were advised to find it on their own. In the middle of the bayou, Louis pricks his foot, forcing Naveen to dive into the waters, himself, to grab the amber, getting stuck in tree roots in the process until he's rescued by Tiana.
Louis also appeared in Something Old, Something New, where he helped Naveen handle the music for his and the Tiana's wedding.
In One Magical Feast, he entertained the guests at Tiana's Christmas party, dressed as Papa Noel (the New Orleans equivalent of Santa Claus) and handing out gifts.
He also assisted Tiana, Naveen, and Charlotte in preparing an Easter parade in A Princess Easter.
Louis plays a major part in the game, which takes place after the events of the film where Tiana and friends are in the mix of transforming the run down mill building into her dream restaurant. Along with many other characters, Louis participates, but is more prominent in the various mini-games that take up most of the game, showing some of the adventures Louis, Tiana, and the others had partaken in during their journeys in the bayou.
Whilst not appearing in the game itself, Louis was commonly mentioned by both Tiana and Naveen during their meet-and-greet sessions with the game's players. He was prominently mentioned during a quest given by Naveen who asks the player to find a replacement band to play for Tiana's Palace as Louis went off on a gator family reunion for a while.2009. He first appeared in Tiana's Showboat Jubilee.
Louis' likeness is also featured at Disney's Port Orleans Resort in Walt Disney World. In Disneyland Paris, Louis, Naveen, Tiana, and Dr. Facilier were featured in the special 2013 event, Disney Dreamers Everywhere!
Tiana's Showboat Jubilee
In the temporary boat show, Louis, Tiana, and Naveen sing various songs from the film. In the middle, Tiana sings about her dream of her restaurant which gives Louis the urge to talk about his dream: to become human.
Along with Tiana, Ray, and Naveen, Louis is featured on Tiana's float, seen dancing along to the bouncy music from the film as the parade proceeds. Like with most of his live roles, Louis is featured with his trumpet.
In Walt Disney World's Frontierland, Louis assists Mama Odie and the guests in their quest to foil Doctor Facilier, who has been revived from the dead by Hades. Louis is first heard alerting Mama Odie about Facilier busting Lawrence out of jail and is later seen alerting Mama Odie about Facilier kidnapping Tiana. Later on, Louis assists the guests when battling Facilier for the crystal of the Magic Kingdom. After Facilier is defeated, Louis retrieves the crystal so it can be returned to Merlin.
- In the chapter book continuation of the film The Grand Opening, it is revealed that Louis named his trumpet Giselle, and that he's unable to perform without it, becoming a nervous wreck when the instrument is briefly lost.
- Originally, Louis was meant to be introduced after Ray, but the filmmakers felt doing so would make Louis seem like an interruption and decided to swap the introduction in order between the two sidekicks.
- He is the first crocodilian character in a Disney film to be friendly in nature since Ben the dancing alligator from Fantasia.
- In some screenshots, it is shown that Louis has green eyes.
- Despite the fact that alligators have incredibly thick skin and can recover very effectively from serious injuries such as broken legs, Louis has a very low tolerance for pain as shown when he screams in agony when a pricker sticks to his finger, and when more are pulled out of his body.
- When Louis says, "All kinds of hoodoo," he grabs some vines and widens his eyes like Madam Mim does, with her hair, and he even resembles her a bit when he does that.
- Louis shares the same first name with Louis Armstrong, a famous trumpet-player from the time period that the film takes place in (1920s). The alligator may have been named after him.
- Armstrong is also referenced in the song "When We're Human" from the film.
- Louis bears some resemblance to Steven, an alligator from 101 Dalmatians: The Series.