Yakko, Wakko, and Dot, the "Warner Brothers (and the Warner Sister)", were voiced by Rob Paulsen, Jess Harnell, and Tress MacNeille. Yakko (the oldest child) is a wise-cracking smart-aleck and usually acts as the leader of the trio; Wakko (the middle child) has a Liverpool accent, a huge appetite and a gag bag filled with tricks, and Dot (the youngest child) is cute and sassy.
Their personalities in comical-humor-wise are similar, yet unique, mostly if not counted comic-wise. In the show, the siblings often appear in other characters' skits, usually chased by Ralph the security guard; most other characters are confined to their own segments. They are usually referred to as the "Warner Brothers and the Warner Sister" if all three, though since one is female, the proper term is actually "Warner siblings". Their last name "Warner" is named after the real-life studios "Warner Bros." or "Warner Brothers". They were drawn in the "Warners Studio" supposedly their age from Yakko to Dot, oldest-to-youngest are labeled in age by who was drawn first, middle, and last; at least because the theme intro shows Yakko being drawn first, Wakko middle, and Dot last. The show usually follows these characters' zany skits, and usually portrays them to have low intelligence. However, this may only be internal whit and the ability to see the humor in every situation around them, never taking anything seriously. (They are regularly shown to be very clever and knowledgeable in many areas, usually causing events that should have been impossible to predict)
Yakko, as his name implies, is the most talkative and quick-witted of the Warner siblings. Like his siblings, Yakko is an ambiguous dog-like cartoon character. He is the tallest of the three, and wears khaki pants up to his waist with a large belt. Like his siblings, he also has short black fur covering most of his body and white fur over his face, cheeks and eyebrows. His eyes are black and he has a small red nose, black ears, as well as a tail that sticks out through his pants. He was also seen with an addition of a green scarf in the movie. He also (along with his other siblings) can be seen with different attire in specific episodes (like "Roll Over Beethoven") such as top hats, sashes, suits, etc.
It also seems as though he can store a variety of items within his pants (including a yak), much like Wakko does with his "Gag Bag". He doesn't seem to do this as much as Wakko. Yakko is the oldest of his siblings, though his age is never revealed in the show (according to Tom Ruegger, Yakko is 14).
He is the same species as the other Warners and is a little taller than Dot. 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 keeps on even when he does another costume. He also does not wear pants on most occasions, often joking about this aspect.
Dot is of the same species as her older brothers. She wears a pink knee-length skirt, frilly pink or white panties, has hair resembling that of Uran from Astro Boy and a yellow flower tie in her ears. In Wakko's Wish, she gets a beauty mark that she calls a "cutie mark" ("Cindy Crawford, eat your heart out!" she remarked). However, this "cutie mark" only appeared in the movie. Whenever Yakko and Wakko introduce themselves by saying "We're the Warner Brothers!", she always follows with "And the Warner Sister!" Her full name is "Princess Angelina Contessa Louisa Francesca Banana Banna Bo Besca the Third" (a reference to Pippi Longstocking's long real name, "Pippilotta Delicatessa Windowshade Mackrelmint Ephraim's Daughter Longstocking"), which is the reason why some fans call her "Princess Dot" for short, as revealed in Wakko's Wish. (Her last name is Warner, but is not added to her full name.) According to Tom Ruegger, Dot is 5 years old.
Yakko is intelligent and well-read. Out of the three Warners, Yakko is the leader, taking charge of most situations, and Wakko and Dot look up to him. Being the oldest, much of the adult humor comes from him (though whenever it comes from anyone else, Yakko quickly pipes in with "Good night, everybody!")
Yakko and his brother Wakko are infatuated with the beautiful Hello Nurse. Whenever they spot her or another attractive woman (or Minerva Mink), they react in an exaggerated manner (for example, howling like wolves) and shouting "Hell-O-o, Nurse!" This is usually followed by them lunging into her arms and giving her a large smooch. They also add some kind of title to "Helloooo Nurse!" in some episodes. Like in "Cookies for Einstein" when they see a Swiss girl selling chocolate, Wakko shouted "Hellooooo Swiss Nurse Miss!" (a play on the hot chocolate brand).
Among Yakko's abilities include a fluent understanding of the Japanese language and wielding two paddleballs at once. He is "the very model of a cartoon individual" according to the song of the same name in the cartoon "H.M.S. Yakko".
He is the 'guardian' of the trio, or the parental figure, as he seems to take charge in many situations, and acts generally in a father-manner towards his siblings. However to Wakko and Dot, he can be seen to argue with or tease them like an older brother (typically) does as shown in the song "I'm Mad". However, when the need arises, he is loyal and protective.
He knows his limits and, while he will tease some people, he knows what to say and when to employ diplomatic charm to calm them down - or at least try to. This can be seen when he interrupts Dot's "I'm Cute" song, but notes that she is "awfully cute" when angered. He deeply cares for Wakko and Dot, which is seen in Wakko's Wish, as well as some episodes in the series.
He's the middle child (in the song "Hello Nurse" he says he's "seven" to rhyme with "heaven," though according to Tom Ruegger, Wakko is actually 11), and the weirdest and most absurd of the bunch, hence his name. He 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 just raised the pitch). He often carries a "Gag Bag", from which he can produce objects 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). He 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 (hence the first syllable in his name being "Wak").
Wakko is very flexible (there are a few episodes where the others make use of him 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 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. According to the song "Hello Nurse" he is 7 years old; this was the only reference ever made to their age, and was not considered canonical by the writers.
His cap is his trademark; when the Warners wear costumes, Wakko will usually keep his cap on, which holds Elvis Presley hiding in the cap's hammerspace. Occasionally, he'll take it off, which makes him look very similar to Yakko, as seen in various episodes and the movie Wakko's Wish, of which he is the main protagonist. 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, and in some segments, he doesn't say anything 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.
Extremely cute, beautiful and thoroughly aware of it, Dot is very confident, but a bit vain and selfish at times. She is arguably the cutest one; she even sings a whole song about how cute she is in the episode "I'm Cute". She is also the most overtly aggressive. As she says in the first episode, "Call me Dottie, and you die." However, she's been called Dottie a few times and the source remains unharmed, but this is not always true. In one episode, she throws a bomb at Yakko and Wakko for calling her that. She often makes note of Wakko's ridiculous and disgusting eating habits (even saying he went too far when he ate the moon in one episode), going "DIIIIIISGUSTING!" whenever he eats something unappetizing. She is easily miffed at her brothers' reactions around females; afterwards she often says, "Boys: go fig." She loves her brothers dearly, but their behavior (notably around women) often annoys her.
However, even though she views Yakko and Wakko's behavior around beautiful women repugnant, she has reacted similarly to attractive men, most notably Mel Gibson (she said she would "marry that man"). Dot also carries around a pet, contained within a tiny box that is revealed to be a horrifying monster much too large to have fit inside the box. In one episode, one of her pets ends up marrying a Xenomorph. She also seems to have a sense of humor much like her brother Yakko. But, like Wakko and his hat, even when Dot is in a costume she usually has a little flower in her ears or hat (unless she is in her pajamas and/or going to sleep, then she wears curlers). Her voice is like that of Babs Bunny (also voiced by MacNeille) and later Fang on Dave the Barbarian, but with a younger, sweeter tone to match with her apparent age as the youngest sibling. Also, as explained in the Wakko's Wish, it has been discovered that Dot was born from a beautiful flower in a garden on the first day of spring. However, when Yakko tells her this story at bedtime, it sounds fictional.