Sheldon claims his hair grows at 4.6 yoctometers/femtosecond. That converts to 1.2 cm in 30 days which is consistent with normal hair growth rates.
When Leonard mentions changing reality by going back in time and killing a bug, he is referring to a short story "A Sound of Thunder" by Ray Bradbury about a sportsman going back in time to shoot an already doomed Tyrannosaurus rex and steps off the designated path, kills a butterfly changing the history/reality of his time.
Howard experiences zero gravity in an airplane that flies straight up into the air and then straight back down. He says he threw up during the experience. For this reason, astronauts lightheartedly call this airplane "The Vomit Comet."
At one point while talking to Bernadette about astronaut training, Wolowitz makes a reference about attending sunset Sabbath Services at "Camp Hess Kramer". This is a real camp operated by Wilshire Boulevard Temple in Los Angeles and has been in existence since the fifties.
Sheldon says that he can't go to Supercuts anymore because he can't stand male and female hair being cut in the same room. In a previous episode (The Friendship Contraction) it was one of the places he needed to have someone take him, so that must have been when his aversion started.