Terrance and Phillip are a Canadian comedy duo, and stars of The Terrance and Phillip Show, a show-within-a-show on South Park. The show serves an interesting role; the parents of the South Park characters view Terrance and Phillip's obsessive fart gags in much the same way that many parents in the real world view South Park - with considerable contempt.
Please visit their article on the South Park Archives for more information.
Phillip (Sir Phillip Niles Argyle of Montréal) has blond hair and a blue shirt with a "P" while, Terrance (Sir Terrance Henry Stoot from the "small village" of Toronto) has black hair and wears a red shirt with a "T". Like virtually all Canadians in South Park, they are geometrically-figured with small beady eyes and egg-shaped heads which flap up and down whenever they speak.
Terrance and Phillip have heavy accents, ostensibly to represent stereotypical American views of Canadians. The "aboot" pronunciation has also been used in The Simpsons and Canadian Bacon. The fact their career is based on an accidental fart Phillip made on the The Ed Sullivan Show at the age of six, because that was the only part of their act Americans understood, may be saying something about Canadian perceptions of Americans.
Terrance used to date Canadian pop vocalist Celine Dion, and had a daughter with her. Their daughter, named Sally, is very close to her father and was an illegitimate birth, as Terrance refers to her as "my bastard daughter".
In the episode "Eat, Pray, Queef", Terrance and Phillip are married to the Queef sisters, Katherine and Katie.