At the murder mystery party, the cast is each wearing one of the classic Clue character colors: Raj is Mrs. White (off) white, Penny is Mrs. Peacock blue, Leonard is Miss Scarlet red, Bernadette is Colonel Mustard yellow, Amy is Professor Plum purple, and Stuart is Mr/Rev Green green.
The Buzz Aldrin bobble head that Howard buys for Sheldon is seen on Sheldons desk at the university in later episodes.
The Star Wars sheets seen on Sheldon's childhood bed at his mother's house are the same sheets he bought from The Pottery Barn prior to the start of The Euclid Alternative (2008) and spent the first few scenes trying to return them because they were "too stimulating".
In the future they show a tiny, silvery, parked car. That is an early prototype of the all electric Sparrow developed by Electra Meccanica. Parked in front of it is a production model electric BMW i3. The car which drives past is the Nissan Resonance concept car from 2013.
Leonard remarks that Raj's murder mystery is essentially a rip-off of the time-travel murder plot from The Terminator (1984), to which Raj retorts that The Terminator was ripped off from an The Outer Limits (1963) episode written by Harlan Ellison, namely Demon with a Glass Hand (1964). Leonard responds by saying it was actually the episode Soldier (1964). Basically this is true, but it is even more complicated: Ellison indeed sued the studio of The Terminator for perceived plagiarism of his screenplay for 'Soldier' (but not 'Demon' as is often claimed). James Cameron, writer/director of The Terminator, denied this, and was prepared to take the case to court. However, the studio warned him that he himself would end up paying for all financial damages, in case he would lose. Cameron, who was still struggling as a filmmaker at the time, could not afford to take the financial risk, and was forced to settle the case out of court. Later prints of The Terminator therefore recognize Ellison's input. Cameron still maintains that he conceived the story himself, and that Ellison (who was notorious for his copyrights infringement lawsuits) was just trying to take credit where it wasn't due. (source: www.jamescamerononline.com/Ellison.htm)