The biggest of the "It's Showtime" kids is right up in the face of the old man with the guitar who got on the train at the same time - something about "respect" and something about being "grown." Katie booed as soon as the Showtime kids came on the train, so they're already feeling a little like they've got something to prove.
And now she's talking back to Showtime as they get off at the next stop after they've threatened to follow the guitar guy around until he goes home. The conversation goes about as well as you'd expect, with the kid in the Spongebob Squarepants backpack howling "Suuuck my diiiiiiick!" from the platform as the doors close.