Wakko is the same species as the other Warners and is a little taller than Dot, but he is about the same height as Buster Bunny. Wakko is arguably the most animalistic of the trio, as several segments have him behaving like a dog - walking on all fours, doing tricks for treats, etc. He is the only one of the three that wears a shirt and has a red hat, which he wears even with other costumes. He also does not wear pants on most occasions, often joking about this aspect.
In the song "Hello Nurse" he says he's "seven" to rhyme with "heaven," though according to Tom Ruegger, Wakko is actually eleven. This was the only reference ever made to his age, but was not considered canonical by the writers.
He is also known as The Great Wakkorotti, in this personality he performs songs by belching to a tune. Afterwards, as the audience throws roses onto the stage and applauds, he says "excuse me!"
Wakko is the middle child and the weirdest, most immature, and most absurd of the bunch, hence his name. Wakko speaks with a Scouse accent that Harnell explicitly modeled after Ringo Starr; initially Harnell created a John Lennon-esque voice for Wakko until he saw that the character was short, so he changed it to a Ringo Starr-esque voice which he later raised the pitch. Wakko often carries a "Gag Bag", from which objects can be produced as needed, and also uses a large mallet when situations call for it. More often than not, his tongue is sticking out of his mouth; it will hang out at any given moment. Wakko generally supplies the more crude humor, which Yakko will often react to. He is the most physical of the three, and thus tends to lean toward physical humor. Wakko is very flexible; there are a few episodes where the others make use of Wakko for ladders and measuring tape. Wakko appears to have a voracious appetite in the show, and will eat almost anything, including gum found under a seat and even rocks for shock value or perhaps simply to see how they taste. He also has a terrible fear of clowns. He's a big fan of Don Knotts from The Andy Griffith Show and, like his brother Yakko, he will also hit on any girl despite his young age. Like Yakko, he has a catchphrase: "Faboo!" meaning fabulous or great. Often, his siblings use variations of "faboo", as in calling a male antagonist "Dadoo" to annoy them.
Wakko's trademark is a cap; when the Warners wear costumes, Wakko will usually keep his cap on, which holds Elvis Presley hiding in the cap's hammerspace. Without the cap, Wakko looks very similar to Yakko, as seen in various episodes and the movie Wakko's Wish. He follows in Yakko's footsteps by singing all the fifty US states and their capitals, in "Wakko's America". Wakko is usually the least talkative of the three unless he is the main character; in some segments saying nothing at all. He also appears to be the most musical as well, being able to belch pieces of classical music (under the stage name "The Great Wakkorotti," with Maurice LaMarche providing the belches), play both the violin and the piano, and get behind a drum kit to deliver the occasional sting after a punchline. In the episode, "Chalkboard Bungle", Wakko can impersonate Ray Charles pretty well. His musical abilities, penchant for physical comedy, and usual quiet attitude seem to reference Harpo Marx.
- Tom Ruegger once stated in an interview that his species was Cartoonus characterus.