muck up

verb

1. To ruin unintentionally.

   “The terrorists have really mucked up our holiday plans.”

   “That’s why they’re called the Founders? Yes, because it will be their job to repair a world that millennials have mucked up beyond repair.”

2. To clown around; to have fun, often at the expense of others.

   “It's the last day of school and everyone is mucking up.”