Tweety is an animated character, a yellow canary bird in the Warner Bros. Looney Tunes and Merrie Melodies series of animated cartoons. His characteristics are based on Red Skelton's famous "Junior the Mean Widdle Kid". He appeared in 46 cartoons during the golden age, made between 1942 and 1964.

Despite the perceptions that people may hold, owing to the long eyelashes and high-pitched voice (which Mel Blanc provided), Tweety is male although his ambiguity was played with. For example, in the cartoon "Snow Business", when Granny entered a room containing Tweety and Sylvester she said: "Here I am, boys!". Another confirmation that Tweety is male comes from the cartoon Greedy for Tweety in which during a hospital stay, Granny (portrayed as a nurse) utters "Oh the poor little Tweety bird, let's makes him a little more comfortable", as she adjusts his bed. Nonetheless, a 1952 cartoon was entitled Ain't She Tweet. His species has been ambiguous across various depictions; although originally and often portrayed as a young canary, he is also frequently called a rare and valuable "tweety bird" as a plot device, and once called "the only living specimen". Nevertheless, the title song of The Sylvester & Tweety Mysteries directly states that he is a canary. His shape more closely suggests that of a baby bird, which is what he was during his early appearances (although the "baby bird" aspect has been used in a few later cartoons as a plot device). The yellow feathers were added, but otherwise he retained the baby-bird shape.

In his early appearances in Bob Clampett cartoons, Tweety is a very aggressive character who tries anything to foil his feline adversary, even kicking the cat when he is down. One example of a malicious moment is in the cartoon Birdy and the Beast, where a cat chases Tweety by flying until he remembers that cats cannot fly, causing him to fall. Tweety says sympathetically, "Awww, the poor kitty cat! He faw down and go (in a loud, tough, masculine voice) BOOM!!" and then grins mischievously. A similar use of that voice is in A Tale Of Two Kitties when Tweety, wearing an air raid warden's helmet, suddenly yells "Turn out those lights!"

Tweety's aggressive nature was also initially characterized by Friz Freleng when he began directing the series, but would later be toned-down to instead have him be portrayed as a cutesy bird usually going about his business, and doing little to thwart Sylvester's ill-conceived plots, allowing them to simply collapse on their own; he became even less aggressive when Granny was introduced, but occasionally Tweety still showed a malicious side when egged on. Despite this, in comparison with other major Looney Tunes protagonists such as Bugs Bunny and Foghorn Leghorn, Tweety was not given a complete character arc, instead embodying the "innocent child" role offsetting the motives of his superior Sylvester and their guardian figure.

Bob Clampett created the character that would become Tweety in the 1942 short A Tale of Two Kitties, pitting him against two hungry cats named Babbit and Catstello (based on the famous comedians Abbott and Costello). On the original model sheet, Tweety was named Orson, which was also the name of a bird character from an earlier Clampett cartoon Wacky Blackout.

Tweety was originally created not as a domestic canary, but as a generic (and wild) baby bird in an outdoor nest: naked (pink), jowly, and also far more aggressive and saucy, as opposed to the later, better-known version of him as a less hot-tempered (but still somewhat ornery) yellow canary. In the documentary Bugs Bunny: Superstar, animator Clampett stated that Tweety had been based "on my own naked baby picture." Clampett did two more shorts with the "naked genius", as a Jimmy Durante-ish cat once called him in A Gruesome Twosome. The second Tweety short, Birdy and the Beast, finally bestowed the baby bird with his new name, and gave him his blue eyes. After the first three cartoons, censors declared that the character was nude, and they made the studio paint him yellow to make it look as if he was covered in feathers. The change made Tweety look like a regular yellow domestic canary.

Many of Mel Blanc's characters are known for speech impediments. One of Tweety's most noticeable is that /s/, /k/, and /g/ are changed to /t/, /d/, or (final s) /θ/; for example, "pussy cat" comes out as "putty tat", later rendered "puddy tat", "Granny" comes out as "Dwanny" and "sweetie pie" comes out as "tweetie pie" (a phonological pattern referred to as 'fronting'), hence his name. He also has trouble with liquid consonants: as with Elmer Fudd, /l/ and /r/ come out as /w/. Some of his cartoons feature him singing a song about himself, "I'm a tweet wittow biwd in a diwded tage; Tweety'th my name but I don't know my age, I don't have to wuwy and dat is dat; I'm tafe in hewe fwom dat ol' putty tat". (Translation: "I'm a sweet little bird in a gilded cage; Tweety’s my name but I don’t know my age, I don’t have to worry and that is that; I’m safe in here from that old pussy cat") Aside from this speech impediment, Tweety's voice is that of Bugs Bunny, one speed up (if The Old Grey Hare, which depicts Bugs as an infant, is any indication of that); the only difference is that Bugs does not have trouble pronouncing /s/, /k/ and /g/ as mentioned above.

Clampett began work on a short that would pit Tweety against a then-unnamed, lisping black and white cat created by Friz Freleng in 1946. However, Clampett left the studio before going into full production on the short (which had a storyboard produced, where it was titled "Fat Rat and the Stupid Cat"), however Freleng would use Tweety in his own separate project. Freleng toned Tweety down and gave him a cuter appearance, resulting in his long-lashed blue-pupil eyes and yellow feathers. Clampett mentions in Bugs Bunny: Superstar that the feathers were added to satisfy censors who objected to the naked bird. The first short to team Tweety and the cat, later named Sylvester, was 1947's Tweetie Pie, which won Warner Bros. its first Academy Award for Best Short Subject.