Director Mike Mitchell said:
Shrek is feeling over-domesticated in the fourth installment. He has lost his roar. It used to send villagers running away in terror. Now they run to him and ask him to sign their pitchforks and torches.
To regain his ogre mojo, he strikes a deal with Rumpelstiltskin, the wee troublemaker who popped up briefly in Shrek 2 and 3.
It has been rumored that Paul McCartney voices the vile schemer, but it is actually non-Beatle Walt Dohrn, the film's head of story, who does the honors.
Mike Myers, Eddie Murphy and Cameron Diaz are back as the voices of Shrek, sidekick Donkey and ogress wife Fiona.
Comedians Kathy Griffin and Kristin Schaal are joining the voice cast as witches who hunt ogres. On the side of good is an underground resistance group led by Jon Hamm of Mad Men, who plays "the best-looking ogre you've ever seen," Mitchell says.