This is almost certainly illegal. If the hats actually hit anyone, it's possible to be sued for reckless endangerment and/or assault. If they don't, it's littering.

If you're asking dumb things like "how could a propeller hat dropped 50+ feet hurt someone?" then I encourage you to imagine getting hit in the eye by the spinning propeller if you happen to look up.

Why would this be illegal?

Like there would be a law against lowering hats on a string? I think it may be more funny to have a government create such a law.

Everyone doing this seems wonderful.

You're asking why dropping things out of a window in midtown Manhattan might be illegal?

It's a boring question anyway; this is HN.

The prop on the hat acts as a para-shoot slowing down the hat via auto rotation.

It's the same behavior that a helicopter would have if it was doing an emergency landing as well.

Oh man people will argue about anything. You had to change "dropping things out of a window in midtown Manhattan" (fairly high up as we see) to "dropping things" even to argue :)

> the details would affect whether someone [sic] is illegal

Yep, that's how we apply laws.

Who cares? I assume most people here are grey/blackhats (rainbow in this case).

Well, it's not carefully lowered down on a string, it's dropped from the height of the window, which you can see in the video.