It's Lord Hater’s birthday and Lord Hater hosts an event in his new Doom Arena in which he gets to defeat Wander and see him cower in fear. Wander wants to make the party more special and tries constantly to get Lord Hater to approve of his activities all while fruitlessly waiting for a smile from him.
Peepers blows a party blower at Lord Hater, wishing him a happy birthday and shows that he and the other Watchdogs chipped in and got him his own Doom Arena. But that's not all, and he states the next gift will be sure to get him happy, and reveals Wander and Sylvia in the arena, the former thanking him for inviting them to the party. Lord Hater instantly brightens and proclaims this is his best birthday ever, and has a monologue that what he wanted is to see his most despised enemy cower in fear. He then takes one look at Wander on the jumbotron and obviously sees he's not scared at all.
On the arena grounds, Sylvia attempts to escape, but Wander tells her the party isn't that bad but is poorly decorated. To his worry, Lord Hater is obviously not enjoying the party. He has a monologue similar to Lord Hater's earlier, stating that they need to stay and make sure Lord Hater has fun and replaces his frown with a smile.
Peepers initiates the first event: a myriad of Watchdogs clad in gladiator armor. Wander believes they're more party guests and wonders what they're gonna do for fun. Sylvia suspects they'll crush them into a fine paste, which gives Wander an idea. He asks her to make sure the Watchdog Gladiators don't see anything while he works, and she is proud to do so. She beats up the Watchdogs one by one, and Wander makes a piñata in the shape of Lord Hater's head. Sylvia leads the Watchdogs to the pinata, where they unknowingly burst it open and candy flies out, and they excitedly go for it, much to Lord Hater's anger. Peepers searches for another event but takes a long time, leaving Lord Hater to search for it himself.
Wander notices that Lord Hater wasn't happy with his idea, just as a giant laser shaped like a bottle rises out of the ground. Wander sees this as a Spin the Bottle game and is delighted that Lord Hater chose this. He has Sylvia kick the bottle while he sits on it, waiting for it to stop. The bottle lands on a Watchdog vendor in the stands, but Sylvia kicks it over to Lord Hater. Wander asks Lord Hater to pucker up and awaits for a smile from him, and blows a kiss just as the laser goes off. It ends up bursting away part of the box seat Lord Hater is in and burning him. Sylvia laughs at this, but Wander is sad that Lord Hater didn't smile at this.
Peepers tells Lord Hater that he's sorry the party isn't going as planned, and recommends "the big red button in the upper right corner". Lord Hater presses this, which releases a monster, Sylvia proclaiming this is no party game. She charges for the monster, but she gets beaten by it and thrown into the audience. Lord Hater mocks Wander that Sylvia is not there and wonders if he's scared, and prepares for the fear. The beast charges for Wander, who tames it with a pair of dog biscuits. The Watchdogs enjoy this, but return to their usual jeering when Lord Hater glares at them.
Lord Hater is angered that Wander has not even been scared throughout, which is what he wanted for his birthday, and he decides to do this himself. As he stomps into the arena, Sylvia knocks Peepers out, causing him to activate every button on the control panel which makes the lights change and every obstacle in the arena to show up. Wander takes Lord Hater on a wild run around the arena using the obstacles as party games: The bottle laser as Limbo, a bomb as Hot Potato, and a lava pit as Musical Chairs. Lord Hater fails at every one of them, and Wander challenges him to a race to the end, but stops just before the finish to let Lord Hater win at least once. The moment Lord Hater finishes, he gets beat up.
Lord Hater tiredly says to Wander that he should've been afraid, and Wander sadly explains he is, but adds he's afraid that Lord Hater is not enjoying the party. This gives him one more idea, and he knows how to save the party and finally get Lord Hater to smile. A celebratory musical number led by Wander follows, with Sylvia and the Watchdogs joining in eventually. During this, Lord Hater hesitates and finally gives in to Wander's idea and forces a smile onto his face, much to everyone's delight. Wander and Sylvia depart, happy that their work is done.
As Wander wishes Lord Hater a happy birthday, his face drops into a frown, ending the episode.
Hater, still with a frown, stays in his chair as Peepers cleans and whistles "Your Happy Birthday Song". After a while the monster arrives and roars at Hater before trying the cake, liking it instantly. Hater pets the monster and is then nearly eaten by it afterwards.
- Jack McBrayer as Wander
- April Winchell as Sylvia
- Keith Ferguson as Lord Hater
- Tom Kenny as Peepers
- Fred Tatasciore as Pit Monster
- Doom Arena
- Your Happy Birthday Song
- Wander's banjo head is dented in the center and has a star on the back, like what it looked like in "The Box". In other episodes, it's flat and has no star.
- The monster hides in the stands when all the obstacles come out, but in several establishing shots of the stands and arena, the monster isn't there.
- When Sylvia begins her solo, Lord Hater's arm overlaps her snout.
- When Wander sings "It's Your Happy Birthday" while hanging flags, his mouth isn't moving while he's singing.
- The chest Sylvia gets the cannon out of isn't seen in any shot before or after she uses it.
- Wander puts glitter on the piñata, but when he shows it later, it doesn't have any visible glitter on it.
- The bottle laser is on the far side of the arena, but when Sylvia spins it, it seems to be in the center.
- While Lord Hater is looking at the obstacles as they appear, Wander's mouth briefly turns purple.
- The flags Wander put up permanently disappear after just one shot of them.
- While Wander is shaking his butt the third time he sings "Here's your happy birthday song", he turns around, but his feet are still facing front.
- When Wander wheels Lord Hater's birthday cake over to him, the balloons on either side of Lord Hater's throne are gone.
- When Lord Hater's throne gets shattered in half, the pattern on it changes between scenes.
- When Wander and Sylvia are about to leave after Lord Hater finally smiles, Lord Hater's eyes are white instead of green.
- Wander and Sylvia are on either side of Lord Hater after he forces a smile, but when the camera zooms back in as they leave, they are both on Lord Hater's right.
- When Lord Hater gets his cake, his arms are folded, but after he forces a smile his arms are at his sides.
- When the camera shows Wander as the monster stares at him, Wander's left leg is superimposed over the outline of his fur.
- When Wander is about to sing "It's your happy birthday" the third time, his upper hair strand briefly overlaps his right eye.
- When the camera zooms in on Lord Hater while Wander and Sylvia are singing beside him, Sylvia's rein is missing but reappears when she turns her head.
- Surprisingly, even though Lord Hater wants to see Wander get scared, he doesn't care about Sylvia getting scared at all nor does he try to get her scared. This could possibly mean that he doesn't care about scaring her as much as Wander.
- When Wander says "Just the pit monster!" the white circles on his banjo are brown and the inlays are white.
- Twice in the song, the back of Wander's banjo is darker in color.
- Wander plays the kazoo from the wrong end.
- During the close-up shot when Wander explains the real reason why he was afraid to Lord Hater, when he finishes talking his upper hair strand jerks upward a bit.
- The part when Sylvia tries to get the watch dogs to crash into the piñata her stale is gone.
- After the laser is shoot at Hater, his left light bolt is gone.
- In some scenes the watchdogs' hats are gone.
- When Wander spins his mouth with his hands, it overlaps his left eye.
- The title refers to Lord Hater being referred to as "the birthday boy" by Wander. It also has to do with his birthday.
- This episode and "The Hero" aired on Craig McCracken's 43rd birthday.
- This is the first episode in which a character's birthday is celebrated, in this case Lord Hater.
- This is also the first episode where Sylvia sings, and the first time she sings with Wander.
- This is the first episode to not show an overview of the episode's location nor zoom in on it at the beginning.
- It is revealed that every one of the Watchdogs wish for a second eye.
- The fourth wall is broken four times:
- By Wander, who whispers to the audience, "The birthday boy does not appear to be enjoying the festivities."
- By Wander again, who paints the camera screen with paint.
- By Lord Hater, who stares at the screen after Wander tames the monster.
- By Wander a third time, who looks at the camera while saying, "Aw, the birthday boy should win at least one".
- March 21st, 2014 (Disney Channel France)
- April 18th, 2014 (Disney XD Brazil and Latin America)
- June 28th, 2014 (Disney Channel Hungary)
- July 5th, 2014 (Disney XD Poland)
- September 7th, 2014 (Disney Channel Japan)
- September 7th, 2014 (Disney XD Canada)