Plot hole: Gary Winkle appears as the supposed fourth guy from Winterfest, in the first film. He is shown later in this film in the alternate future, and appears to be around the same age as before. Meanwhile, all of the main characters are much older, and Adam's son is already an adult by now. (00:03:00 - 00:41:00)
Plot hole: They have to invent Nitrotrinadium when they travel to the future because it was not invented yet, but was in the Russian drink in 2010, so should have already been available when they travel to the future.