In the final scene Sheldon says that Leonard took him to the barber that day however Sheldon's hair is exactly the same as when they were in the cafeteria and Howard got them to make up.
In the scene where Sheldon talks to Leonard about driving him to work in the morning, Sheldon puts his messenger bag on with the shoulder strap twisted. The camera cuts away and then cuts back seconds later and the shoulder strap is miraculously untwisted.
The brownies Bernadette makes have nuts in them. Since Howard is deathly allergic to nuts she would never have offered them to him.
Sheldon says to Penny that "with her Italian pizza and his Chinese food they could have a Marco Polo Dinner". Traditional Italian pizza didn't exist in Marco Polo's time, as a key ingredient, tomatoes, still had to be imported from the New World. Someone like Sheldon would actually have known and pointed out this.