Update - after cleaning the Evil Genius' room last night, I let him back in. He was amazed and said "Wow, mommy, you did well cleaning my messy room. I'm going to play in here!"
Yeah, I figured it'd be a mess again in a few minutes. But no. It wasn't.
Instead, he played with one toy, put it away, played with another, until bedtime. It was still clean in the morning! He said it was easier to play when he did that. Hmm. I'm looking for the pod.
While I look for where the aliens hid the body, here's a cartoon for you: