No one did synergy in 1999 like Britney Spears and Melissa Joan Hart. That year, Hart starred with Adrian Grenier in Drive Me Crazy, whose soundtrack featured the only acceptable version of Brit's "(You Drive Me) Crazy" — "The Stop Remix!" — and Hart later appeared in the music video.

Spears then returned the favor with a cameo on Hart's "Sabrina, the Teenage Witch" as herself, performing the title song from Hart's film, in an episode that aired a week before the film's release. That kind of cross-promotion could drive anyone crazy.

https://ew.com/tv/britney-spears-best-tv-performances/