Wily probably got talked into it as it being a good/fun experience by Mahra, who accompanied him. Later in life he'd probably go HAM on decorations using weird tech and holograms. Ironically some people would be more scared of him than of any of that.

Polly would LOVE Halloween and take the chance to dress up as some of her favorite musicians, and bring some real ghosts out to play. Definitely snuck out to trick or treat as a kid.