Nathan Fillion for Super

Nathan Fillion ( Firefly ) and Linda Cardellini ( Scooby Doo ) are joining the cast of James Gunn's Super .

Now, we are trying very much to keep our cool, but you know how it is. Fill-o-fans will understand.

The Fill - who also starred in Gunn's previous directing gig Slither - has been cast as the character that inspires the story's lead, Frank (Rainn Wilson) to become a superhero.



Gunn's latest project has cast of big hitters like Kevin Bacon ( Frost/Nixon ) and Liv Tyler ( Jersey Girl ) already on board.

Now he's busy upping the geek-ante with the always awesome Michael Rooker ( Slither ) and Andre Royo ( The Wire ) in addition to Fillion and Cardellini - and our geek-dar is spinning into excitement-overdrive as a result.

Does the line-up have you Gunn-ing for Super ? Let us know below...