i don't think have many silly headcanons that make me laugh? honestly i can't recall any right now that's how scarce they are.

but i do find many things hilarious when it comes to them and what oda does with them. my fondness for the characters made their gags 1000% funnier than they should be solely because i love reading about them blorblos being silly guys, especially when it's tiny stuff happening in the background. i was laughing my ass off while reading the beginning of jaya arc and watching an octopus stick to zoro the entire time just for them to bring it to surface and sanji to fucking cook it. i like when oda adds random stuff like that.

i also find it hilarious when fanfic authors combine their own flavor of comedy with one piece's canon gags and make their own thing out of them. i just love crackfiction! but i'm not used to come up with stuff myself, at least not memorable ones.

this is very a non-answer to your question anon of mine, but that's just who i am as a person i fear.