From first episode of first season of The Big Bang Theory, it is shown that Sheldon has an attachment to his spot on couch and does not let anybody sit on it. However, in Bat Jar Conjecture, we can see Leonard sitting in his spot and he was on chair. How come he does not stop Leonard from sitting in his spot?
There is another instance. In first episode of season two, Raj was sitting in his spot.
In the Earworm Reverberation, he says that he is very protective of this while making a video. We have clearly seen him show utter intolerance when anybody tries to sit there. So, why does Sheldon not stop Leonard from sitting in his spot on the couch?