Are we counting every sitcom parody of it's a wonderful life?
because I loved it when they did that on Benson.
Glee did a great It's a wonderful life last Christmas where we see how everything would have been frakked up if Artiie hadn't been in a chair.
There's this Episode of Mad About You were Jaimie and Paul defy the Greek and Roman gods (Who knew THEY were real?) saying that if they hadn't met when they did, their intense love would still over come every obstacle.
7 Days had a mirror universe episode and it was just a fricking cartoon.
I loved the Stargate Continuum Movie where Carter is saying "Blah, blah, yaddah yaddah, this is what we have to do to correct the time line" and Beau Bridges replies "I CAN NOT BELIEVE THE ARROGANCE OF YOU PEOPLE!"