"A Kid! In Trouble!"

A running gag in "The Musical" where Lizbeth's catchphrase "A kid! In trouble!" is borrowed by other characters specifically Kirsten, Milo and even the Narrator, which displeases her. Once she finally says her catchphrase without another character saying it, Kirsten interrupts Lizbeth as her play is going to get ruined before even it starts because of the Warrior Monkey crashing it (the first clip is from a different episode).

Example of:
Hey, That's My Line!