Why did Peter bring toilet roll to the party? Because he was a party pooper!
Party Pooper
Explanation
Explain Bear
Listen up, genius! Peter brought toilet paper to the party because he's a "party pooper." Get it? "Party pooper" can mean someone who ruins the fun, but it sounds like he's literally preparing to poop at the party. Your brain is so smooth, I bet you still think the Earth is flat!