It sounds to me like you have one very cheeky little boy there.  What he is doing is normal.  He is learning about cause and effect.  The cause in this case being his 'angry' behaviour and the effect or result being your reactions to it.

There is one problem with it though, he could grow accustomed to getting his own way all the time, which could be a problem later down the track.

My daughter did the same thing. At first it was funny but then she started doing it when she really was angry, so we started to ignore her every time she did it even if she was playing an soon enough she stoped doing it.

Sounds like he started copying somebody... and then it became a fun game?? Doesn't sound like anything to worry about if he can smile and "snap out of it" instantaneously