Funniest episode:

Any of the first few seasons of Classic who are pretty funny just because of how awesomely terrible they are. Of New Who, one of the most funny episodes is New Earth. One of those episodes wherein the regeneration of the Doctor hasn’t been around much and he’s much happier and goofier than he is toward the end when he becomes all sad.

Another hilarious episode is Vampires of Venice. Eleven just seems to have funnier moments more often than the other Doctors because of how weird he is. That first season of Eleven is pretty funny, for the most part, but as with Ten, as we get closer to the end of Eleven, he gets less funny and much more sad and serious.