The title, instead of employing the usual "hare" vs. "hair" pun, is standard spelling, for the expression that indicates thoughtlessness or recklessness.
Elmer is reading a book about hypnotism but he bumps into a bear. He hypnotizes the bear into thinking he is a canary. Bugs then asks Elmer, "What's up, doc?". Elmer states he has him right where he wants him and starts to hypnotize Bugs ("Heh, 'Dracula'", the rabbit observes). Bugs fools Elmer by giving him a balloon with long ears and he hears the bear he hypnotized earlier chirping and falls to the ground. Then he chases Bugs and fights over the gun. Then he cries on a tree and Bugs asks what's wrong. Elmer tells him that he (Bugs) won't cooperate when he tries to hypnotize him. Bugs says he will cooperate.
Then, as Elmer hypnotizes Bugs, Bugs hypnotizes him instead, and commands him to be a rabbit. Elmer then starts to act like Bugs, inducing Bugs to act like Elmer (after furiously declaring, "Who's the comedian in this picture, anyway?"), and the role-reversing chase ensues. Bugs then looks for Elmer, who is right behind him. Bugs talks to the audience while chewing three carrots — two of which are in Elmer's hands. Then the chase starts again, until Bugs has a chance to "un-hypnotize" Elmer. Elmer then runs away and all seems normal. After sneering at Elmer's ability to hypnotize him, Bugs suddenly notices his watch, exclaiming, "I'm overdue at the airport", and proceeds to take off and fly like an airplane. Bugs states "I'm the B-19!" and flies away toward the airport. The cartoon ends with an iris-out.