Why does my toddler think the couch is lava at 11pm?

Every single night right before bed my 2yo decides to jump from pillow to pillow screaming "LAVA LAVA" and it's somehow the funniest thing that's ever happened to her. Wife and I are trying so hard not to laugh because we know we're rewarding the behavior but man it's impossible. This kid is gonna have so much energy when she actually needs to sleep.