Wolowitz teaches Sheldon Mandarin so he can correctly order his Chinese food to make sure he gets tangerine instead of orange chicken. Makes sense to us.
The guys gather round Leonard as he sits in his time machine which arrive. The time machine is, of course, the prop from the 1960 movie that he bought off ebay.
Leonard: We need to widen our circle. Sheldon: I have a very wide circle. I have 212 friends on MySpace. Leonard: Yes, and you've never met one of them. Sheldon: That's the beauty of it
Leonard: At least I didn't have to invent 26 dimensions just to make the math come out. Sheldon: I didn't invent them, they are there! Leonard: In what universe? Sheldon: In all of them, that's the point