Internet Scoop, or Just a Guess

Was that John Barrowman (ARROW, DOCTOR WHO) dubbing Jimmy Fallon in Jimmy's duet with Jay Leno last night? Jimmy can sing but this bit had Broadway quality. Find Barrowman's singing in the movie THE PRODUCERS doing "Springtime for Hitler" and you'll hear the similarity. Plus, he had a show in the UK with a similar theme to the Jay-Jimmy duet. Just saying. This may be the first post on the Interwebs to notice this, or just a bad guess.