The Grease franchise didn't really stop at Grease 2! According to the IMdB, "High School Musical" (2006) has its origins in a 1999 script entitled Grease 3. Britney Spears and Justin Timberlake were to star as the children of Danny Zuko and Sandy Olsson from the 1978 film. The plot was virtually the same as that 'High School Musical', but with more similarities to 'Grease'. The character who would become Sharpay was to be the daughter of Betty Rizzo (producers tried to get Christina Aguilera for the part, but she declined). Timberlake's band-mates from *NSYNC were to have supporting roles. John Travolta and Olivia Newton-John allegedly were approached for cameo roles. But before the script went through a second re-write, the project was shelved until 2004.
http://onscreencars.com/tv/the-homer-the-car-built-for-homer/