The unlikely duo will voice the lead roles in DreamWorks Animation’s upcoming new film Happy Smekday! (Their exclamation mark, not ours.)

Adapted from Adam Rex’s award-winning children’s book The True Meaning of Smekday, the movie casts Parsons as a member of friendly alien race the Boov, who come to Earth to hide from their mortal enemies, the Gorg. 

There he befriends Earth girl Tip (Rihanna), but when he accidentally gives away the Boov's hiding place, the pair are forced to go on the run across a post-apocalyptic United States.

Parsons has previously lent his voice to shows including Family Guy and iCarly, and having played hyper-intelligent Star Trek obsessive Sheldon, the Emmy-winning actor may not find voicing an alien too much of a stretch. The film will be Rihanna's voice-acting debut, though, and the first time the performer has been divorced from her sultry onscreen presence.

Happy Smekday! is currently slated for release towards the end of 2014."