Kyle's adopted brother, Ike, is Canadian.
Terrence and Philip, the boys' favorite t.v. show is Canadian.
Not Without my Anus
When the boys try to create their own circus after seeing Cirque Cheville perform by French Canadians, they recruit the Romania quints from the show. The quints are put on for show similar to the Dionne quints in the late 1930s and early 40s.
When the boys are confronted by Taliban, Stan says that they are from Canada and tells the guys that it is "aboot" time to return to their hooch. Cartman says that he is not "a god-damn Canadian."
In the Philip and Terrence reunion episode, the boys find Philip doing Shakespeare in Toronto. Back in South Park, the boys show "Behind The Laughter" on Terrence and Philip lives. Terrence born in Toronto and Philip born in Montreal went to the Canadian school for Gifted Babies. At age six, they appeared on the Ed Sullivan show (like comedy duo Wayne and Shuster).
In the episode where the boys help Santa, the locater on the sled shows a map of Canada.
In the Simpsons homage episode, they watch an episode of Terrence and Philip where Philip says he killed Celine Dion.