Taylor Momsen

Taylor Momsen

A pair of young-adult television stars are going back in time. Way back.

"Gossip Girl" star Taylor Momsen and "Greek's" Jacob Zachar will join the cast of the comedy "Cavegirl," according to The Hollywood Reporter. "Ghost World's" Thora Birch will step into the fur shoes of the title character.

The movie is based on a BBC television series following teenage Cavegirl, who despite being stuck in the Stone Age struggles with modern relationships and other trials of teen-hood.