Kids wet their beds. So can't it be:
He peed his bed.
He peed in his bed.
What sounds right:#1 or #2? It occurred to me because it's said 'he peed his pants.'
Here's my opinion: without the preposition "in", it needs to be an accident and a place where a pee-accident would commonly happen.
"He peed his pants." "He peed his shorts." "He peed himself." "He peed on himself." "He peed his bed." "He peed in his bed"
All sound OK.
"The poor man was incontinent and accidentally peed his wife's knitting." -- No
S/B: "... peed on the knitting."
"Benny, did you pee my shoes again? You bad dog!" -- No
S/B: "... peed in, or on, the shoes."
The word "peed" is so informal, in some situations it's not even polite to say it. So if you are using it, as long as people can understand you, they probably won't take offense at your prepositions.