Leonard invokes "to boldy go where nobody has gone before" when describing the zero-G toilet Wolowitz designed
Sheldon mentions the Grinch.
Howard mentions that he might run away and live with his Cousin Avi. Cousin Avi is a prominent character in Snatch, although it could be a coincidence.
Wolowitz dumps out a box of spare parts available on the International Space Station required to fix his zero-G toilet much like the Mission Control people did to make a new carbon dioxide scrubber