Bennigan's is a real chain of restaurants. It first appeared in the Season Five episode, "Butters' Very Own Episode". It was seen again in "Professor Chaos" and subsequently mentioned in "Canada on Strike".
Butters has an extreme fondness for Bennigan's. During "Butters' Very Own Episode", his parents planned on taking him there for their wedding anniversary. Later, Butters is seen singing "Happy Anniversary from Everyone at Bennigan's", while receiving a ride from a truck driver.
Bennigan's was mentioned in "Canada on Strike". After a long "strike", the Canadians finally win their benefits, only to receive free coupons to Bennigan's and bubblegum.