Have I mentioned how much I love Jimmy Fallon's musical perfomances? The toy-band version of Idena Menzel's "Let it Go" is fabulous (better than the Oscar performance IMO).
And oh my goodness! The lip-sync battle with Paul Rudd is one of the funniest things I've ever seen!
(his lip-sync battle with Joseph Gordon Levitt is also pretty epic. Look it up. :-)