You mean the Hitler Rap? That's Mel Brooks's version of To Be or Not to Be. Although I don't think the song actually appeared in the final film - it was just used as a promo...
And I have to say the 1942 Jack Benny original version (of the film, not the rap song) is funnier in my opinion.
Not to my knowledge. Anyone who hasn't seen it yet should check out his latest (and sadly last, RIP) film - Lucky. Doing the arthouse rounds about now I think (I saw it on a plane, so not 100% sure).