The title is a play on the phrase "to err is human."
Wile E. Coyote captures his prey, Bugs Bunny, by forcing him into a sack. However, Bugs is easily able to escape his predicament (by producing two holes by his carrot; "What ya got in the bag, doc?" Bugs asks, prompting Wile E. Coyote's long-winded explanation about how he is a genius). The bunny replaces himself with dynamite, and it isn't long before Wile E. Coyote is the victim of a pair of explosions, the second coming when he runs to the elevator. He says to the audience "Poor chap, he had his chance. Now he must take the consequences."
The determined coyote then builds his latest contraption: A do-it-yourself UNIVAC Electronic Brain, which he consults for suggestions in capturing Bugs. The machine provides the recommendations after Wile E. supplies key words.
Wile E. Coyote's efforts include the following:
"Rabbit," "in hole," and "combination lock." The UNIVAC suggests burglary methods, providing a combination to the door of Bugs Bunny's hole. Wile E. Coyote breaks in that night, but slips on a banana peel Bugs nonchalantly places at the base of his hole. The Coyote falls into the Coyote Disposal, which has a coyote-sized opening over an unseen gorge.
"Breakfast," "toaster," and "carrots," resulting in Wile E. Coyote placing hand grenades in Bugs Bunny's carrot toaster. The grenades spring right back at Coyote and explode in his face. Bugs Bunny then quotes "One of these days, I'm gonna have to have that spring fixed."
Upon asking "What now?", Coyote tries a plunger, but Bugs Bunny uses a ventilation pipe to cause his would-be captor to get sucked in.
A recommendation to "slip TNT stick into vacuum cleaner" appears to be the break Wile E. Coyote is looking for, as the live stick is vacuumed up. However, Wile E. Coyote doesn't count on Bugs Bunny emptying the vacuum bag into a garbage can that he is hiding in.
"Well, how about trying a booby trap in the carrot patch?" Wile E. Coyote places a boulder above Bugs Bunny's carrot patch, but Bugs safely harvests the carrot meant to set Coyote loose the trap (wearing a bonnet and bow tie and nonchalantly singing (to the tune of "Time Waits For No One") "Carrots wait for no one, so I'll pick them now / Before they are eaten by some sloppy cow / Carrots wait for no one, so I'll pick them now."). However, when Wile E. Coyote pulls at the trap, it is triggered. A panicked Wile E. Coyote desperately asks the UNIVAC, "Rock," "falling." "What," "do","I," "do?" The answer provides no solace: "Go back and take your medicine." Wile E. goes back and is flattened by the boulder, once and for all.
The UNIVAC's intelligence is then revealed to be Bugs Bunny when the computer screen slides open. Bugs then quotes "Of course the real beauty of this machine is that it has only one moving part."
When Bugs retrieves the banana peel from an emergency alarm box over his bed (which instructs to break glass "in case of coyote"), he is shown breaking the glass with a hammer to retrieve the banana peel, but in the next shot, the box is shown with the glass again intact.
When this cartoon aired on ABC, the following scenes were cut:
Wile E. looking into his sack and being blasted in the face by the detonating TNT inside of the sack.
Wile E. suffering another dynamite explosion in his portable elevator
Two hand grenades dropped by Wile E. into Bugs' toaster popping prematurely into a position beside Wile E. and exploding there
The lit dynamite stick that Wile E. placed in Bugs' vacuum cleaner exploding in the trash can where Wile E. is hiding and into which Bugs dumped the contents of his vacuum cleaner bag.