Christina Aguilera's voice is unmistakable [1], but do you think you'd be able to recognise her in a disguise while performing during your morning commute? Well, the answer for several NYC subway riders on Thursday was no. In a sneak peek of The Tonight Show [2]'s upcoming episode, Christina and Jimmy Fallon [3] go incognito in funny disguises as they treat unsuspecting commuters to a surprise performance of Aretha Franklin's "Think." Between Christina's giant floppy hat and Jimmy's hilarious wig, we have a feeling this is going to be good. Check out a preview of tonight's episode above, then relive Christina's incredible celebrity singing impressions [4].