When Pixar announced they would be doing a prequel to the beloved 2001 hit "Monsters, Inc.," fans were stoked at the chance to see everyone's favorite group of lovably terrifying creatures again. Or more precisely, hear them, as stars John Goodman, Billy Crystal and Steve Buscemi all quickly signed up to reprise their roles form the original.

So that was sweet. But according to Entertainment Weekly, "Monsters University" is actually going to be even sweeter, as a bunch of fan favorites have just signed on to round out the voice cast.

Are you ready for the animated version of Captain Tightpants?

Well, we sure hope so, because "Firefly" and "Castle" star Nathan Fillion is among those who have inked a deal to help tell the story of how Sully and Mike Wazowski first met and overcame their differences to become best buddies. And Fillion isn't alone: "The Office" star John Krasinski is also on board, as is comedian Bonnie Hunt, who has a number of Pixar films already on her resume, including a different role in the original "Monsters Inc."

The additions round out a top notch cast that already includes Dame Helen Mirren, Alfred Molina, Dave Foley ("A Bug's Life," "Kid in the Hall"), Charlie Day ("Horrible Bosses"), Aubrey Plaza ("Parks and Recreation"), Sean P. Hayes ("Will & Grace") and your mom (just kidding).

"Monsters University" is set to hit theaters on June 21. Which may be the most amazing thing about the new cast additions — because for the first time ever, we're actually looking forward to summer school.

Now that's real Pixar magic.