Things You Didn't Know About The Big Bang Theory

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While the gang is decorating the Christmas tree, Sheldon (who is in Texas) video calls Amy.

Amy takes the tablet and shows Sheldon the room. However, nobody seems to detect that Raj is sitting in Sheldon's spot. A few moments later, Raj makes a comment and Amy directs the tablet his way.

Even in such close proximity to each other, neither Sheldon nor anybody else detects that Raj is still sitting in Sheldon's spot.

This goes on throughout the entire episode, even when Raj switches places with Howard.