Episodes like this really frustrate me. "Hey look! Lisa made Facebook, only we WON'T call it Facebook!" That already feels lazy in itself, but it sounds so much dumber when you remember that they already HAD Mark Zuckerberg and the actual Facebook on the show a year ago! They even acknowledged Facebook at the end with the Winklevosses, anyway! So what was the point?
So the laziness of this episode was a real turn-off. Some of the jokes were ok. Even if it was given away in the commercial, I still loved the Angry Nerds bit. But overall, it's a thumbs down for me on this one.
Oh, but the Letterman couch gag was a nice surprise.
The funny thing is, the original BttF uses this science during the demonstration with Einstein. They just threw it out in the sequel so they could write wacky future gags. A lot of the time travel theory in the sequels is based on assumptions.