"Santa`s Dream" joke

Once Santa kept having the same weird dream everynight, so he went to a doctor.
Doctor: What was your dream about?
Santa: I was being chased by a vampire!
Doctor: (giggles quitely) So... what is the scenery like?
Santa: I was running in a hall way.
Doctor: Then what happened?
Santa: Well that's the weird thing. In every single dream, the same thing happened. I always come to this door, but I can't open it. I keep pushing the door and pushing the door, but it wouldn't budge!
Doctor: Does the door have any letters on it?
Santa: Yes it did.
Doctor: And what did these letter spell?
Santa: It said "Pull"