Lou is a stupid, idiotic, naive, and dumb spider unlike his friend, Bud the snake. Bud dislikes Lou's stupidity and shows his hatred by hitting him on the head a few times, even when Lou touches his tongue, which he dislikes as well. Like Bud, he mistakenly refers to his mistress Winifred as "Freddy," which she dislikes being called.
Lou is first seen removing light bulbs of fireflies (referred as lightning bugs) given to him by Bud, who catches them using his tongue like a frog, which are one of the main ingredients their beginner witch mistress, Winifred asked them to bring, which will give her the power to become a real witch.
Without waiting for the arrival of their other friend, a bat named Foxglove, Bud accidentally grabs Zipper and gives him to Lou. Thinking he's a dud, Zipper bites Lou on the nose and flies away. Bud makes Lou forget the idea of getting even with Zipper after having his nose bitten by him and tells him to grab a few more fireflies.
Then, the Rescue Rangers arrive and try to foil their plan but to no avail. Winifred appears and transports them back to their hiding place using a magic flying vacuum cleaner.
At their hiding place, an old Laundromat, Winifred congratulates the "three of them" for a job well done; only for Bud to state that only he and Lou got them and mistakenly calls her "Freddy," which causes her to get angry and zap a few magic sparks at them. After adding the light bulbs to her potion, Winifred asks for the list but Lou accidentally dropped it during his confrontation with the Rescue Rangers. Luckily, Winifred remembers the last two needed "otherwise, she would be very angry" and she flings Bud and Lou into a pile of laundry and goes out for the next ingredient: a chieftain's (in this case, the chief of police) hair.
At night, in a museum, after getting the hair, Bud and Lou rob the last ingredient needed: a piece of the moon (in this case, a moon rock) while Winifred waits outside in the air. After tying up a guard in webs and getting the rock out of its glass case, Foxglove appears, steals their glory, and takes credit, which satisfies Winifred.
The Rescue Rangers arrive to stop Winifred but again to no avail. Luckily, Winifred loses the Moon rock after using it as something to shoot at the Rangers. Foxglove offers to get it back for her, which Winifred agrees to. Just to make sure Foxglove keeps her promise, Winifred watches through a potion only to find the Rangers getting the rock first, so, she decides to take matter into her own hands. After kidnapping Foxglove, Dale, and the rock, Winifred turns Dale into a frog and offers him as dinner to Bud and Lou, but Bud fails to catch him with his tongue due to Zipper dropping a crate on it. When Lou examines Bud's tongue and naively asks if he's okay, Bud whacks him on the head with his tail and states, "Don't touch the tongue!"
When Foxglove, having fallen in love with Dale since they met, threatens to ruin Winifred's spell by dropping a brick into it unless she changes Dale back and lets him live, which she does, Bud catches Foxglove along with the brick in his mouth; much to his agony. After Dale and Foxglove are captured by Lou's webs and are soon to be offered as snacks for them by Winifred, the rest of the Rescue Rangers appear. Lou is defeated when trying get his payback with Zipper. He tries to catch Zipper with his web, only to catch a lid instead, which Zipper pushes aside and allows to fall, thus causing Lou to fall as well.
- Lou was based on and named after the late comedian, Lou Costello.
- His face bears a clear resemblance to Mole from The Wind in the Willows.