The title is another obvious play on "hair", and on patent medicines that had the opposite effect of a "hair tonic" (as with another Bugs title, Hare Tonic).
Elmer tries his best to make one of those "Jekyll and Hyde potions" that "changes a normal character into a devilish fiend", but his experiments always end in failure, causing his test animals to run for the hills and eat grass. He decides to trap a rabbit (Bugs Bunny) as his next subject. After he traps him, Elmer forcefully gives Bugs the potion, again with no success. Elmer has a crying fit until Bugs gives him one of the potions, giving Elmer the same initial looney side effects the other animals had experienced. (Bugs comments to the audience, "I think Spencer Tracy did it much better. Don't you, folks?"). At one point when Elmer experiences the looney side effects of the potion, Bugs flashes rebus picture cards at Elmer showing a "screwball," a "crackpot," a "drip," "bats in the belfry," etc.
When a bear enters the lab from the nearby forest, both Bugs and Elmer mistake the bear for one another and unsuccessfully attempt to "cure" each other with potions, until they discover that the bear is real. Elmer plays dead to fool the bear, and is saved by his bad odor (just as with Wabbit Twouble). Elmer thinks he's safe until he thinks he hears the bear again, but it's Bugs this time, imitating the bear (again, lifted from Wabbit Twouble). Meanwhile the bear is standing on the side of the room watching them, convinced that both Elmer and Bugs are crazy, flashing rebus picture cards to the audience just like Bugs did earlier.
- Elmer seldom referred to his perennial co-star by name, but typically only as "that scwewy wabbit" or similar expressions. This cartoon is one of the few in which Elmer actually acknowledges the bunny's name. When he sees the bear munching a carrot and assumes that it's the rabbit transformed by his drug, Elmer cries with delight, "Bugs Bunny!" In the reverse situation, when Bugs mistakes the bear for Elmer, Bugs still calls him, "Doc!" (Coincidentally, in the aforementioned Hare Tonic, Bugs himself addresses Elmer by name.)
- In the original release of this cartoon there is an abrupt jump cut occurs between Elmer celebrating Bugs' capture and Elmer sternly carrying Bugs to his laboratory. The missing scene is most likely to be lost; as the release on Looney Tunes Golden Collection Volume 3 never restored it. 
- This is Frank Tashlin's last cartoon that he directed before leaving Warner Bros. As such, he is not credited. Also, this short is the second and last short Tashlin directed to feature Bugs Bunny and Elmer Fudd.