1. - Ashley Tisdale, High School Musical, TV, 2006. Disney’s musical franchise - two tele-films and a cinema feature -  grew out of... Grease 3.  In 1999, Britney Spears and Justin Timberlake were signed as the kids of  Danny Zucko and Sandy Olsson from the 1978 filmusical. Re-writes were afoot (to hopefully add Christina to the mix as Betty Rizzo’s daughter) when the idea was shelved in 2004. Apart from obvious and well-greased angles, the script was, basically, what we saw in HSM. 

2. - Katherine Heigl, Knocked Up, 2007.