My favorite one hit wonder was The Insiders, "Ghost On the Beach". That was 1987, so just before the 90s.
Another early one-hit-wonder is from Deee-Lite, "Groove is in the Heart" (1990). I still watch the video from time to time...the woman can dance like no other.
"Doin' the Do" - Betty Boo
"Hippychick" - Soho
"I'm Free" - the Soupdragons
"Unbelievable" - EMF