Premise: "Happy Birthday" is a 1980 song and by The Boys Next Door. It was released as a single on 16 February 1980 on Missing Link. The song is not related to the popular birthday song "Happy Birthday to You". The first album it appeared on was "The Birthday Party". It was later included as track two on the 1992 compilation "Hits".
Hypothesis: A lot of people confuse "Happy Birthday" with "Happy Birthday to You".