In the fourth season installment The Apology Insufficiency (2010), Raj meets Dr. Neil deGrasse Tyson at CalTech and introduces him to Sheldon. Now not only do the two act as though they have never met, but Tyson tells Raj that he kicked Pluto out of the solar system, while in season four he said the decision was made by a group of scientists.
When Mr. Fowler (Teller) leaves Sheldon's and Amy's apartment, he doesn't lock the deadbolt, but seconds later when he comes back after the gang has gone into Leonard's and Penny's apartment he uses the key to unlock the deadbolt.
At about 14 minutes, Amy and Sheldon are on a tour of Tesla's favorite spots. Once they start arguing and the rest of the tour group turns partly around and stare at them. In the following shot, the tour group is completely turned around. Then after Amy leaves they are turned partly around again, facing more towards the front as if they had never turned completely around.