The title is a pun on the term "by a hair," meaning "by a small amount."
Bugs again challenges Cecil to a race after viewing footage from their previous encounter two years earlier (which seems to depict Cecil as having won fairly instead of by cheating Bugs with his cousins). Bugs then goes to Cecil's tree home disguised as an old man (a parody of Bill Thompson's "Old Timer" character from Fibber McGee and Molly) to ask the turtle his secret. Cecil, not in the least bit fooled by the disguise, so tells him he remarks that his streamlined shell lets him win, and produces a set of blueprints for his "air-flow chassis". The turtle ends the conversation with the comment, "Oh, and another thing... Rabbits aren't very bright, either!" just before slamming the door in the enraged bunny's face. Not getting the hint that the turtle's story is a humbug, Bugs builds the device and prepares for the race.
Meanwhile, the bunny mob learns of the upcoming match-up and places all its bets on Bugs. ("In fact, we don't even think that the toitle will finish... Do we, boys?" "Duh, no, Boss, no!") The race begins, and Bugs still outpaces his reptilian rival. However, in his new get-up, the dim-witted gangsters mistake him for the turtle. Cecil reinforces this misconception by dressing in a gray rabbit suit and munching on some delicious carrots. The mobsters thus make the shelled Bugs' run a nightmare, ultimately giving the race to Cecil (in an aside to the audience, as the rabbits cheer him, Cecil remarks, "I told you rabbits aren't very bright!"). When Bugs (who, by this time, realizes he's been had) removes the chassis and sobbingly reveals that he's the rabbit, the rabbit gangsters remark, in mock-Bugsy style, "Ehhh, now he tells us!" and commit suicide by shooting themselves with a single bullet that goes through the sides of all of their heads.
- Bill Thompson's Old Timer character
- The ending where the gambling ring shoots themselves after realizing that they've been trying to sabotage Bugs throughout the cartoon has been cut from many TV prints of this cartoon, including versions shown on the Turner channels Cartoon Network (excluding its appearance on "The Bob Clampett Show"), TBS, and TNT. The scene was also cut when it aired on Turner Classic Movies' animated anthology show Cartoon Alley, but that version uses a fake fade-out after the suicide instead of the iris-out used on TBS and TNT or the dissolve to the dubbed version ending card used on Cartoon Network's non-Bob Clampett Show appearances and currently on Boomerang.
- The TBS version also shortens the part where the rabbits pounce on Bugs before he can reach the finish line.
- MeTV airings of this cartoon left in the suicide end gag, but edited the scene with the newspaper announcement of Cecil and Bugs' race to remove the word "Jap" in the headline about a cruiser being blown up in the Pacific.
- This is the first cartoon to use the modern Bugs Bunny design by Robert McKimson, though it's not until the late-1940s where all the animation directors of Warner Bros. Cartoons finally settled on using McKimson's Bugs design from this cartoon.
- The film is a sequel to Tex Avery's 1941 Merrie Melodies short "Tortoise Beats Hare", also starring Bugs Bunny and Cecil Turtle. Bob Clampett took Avery's scenario and altered it for this film.
- Adolf Hitler's name appears on the newspaper in a news story about Hitler committing suicide, which didn't happen until two years after this cartoon was released.
- Michael Sasanoff's name appears on the blueprint.
- The USA dubbed print uses the 1947-48 end card and retains the original 1941-1955 MM ending music cue while the EU dubbed print uses the 1937-38 end card with 1938-41 MM ending music cue.