What Happened When a Comet Hit Jupiter?

A comet can hit a planet we saw in the 90s it hit Jupiter. And it could hit us and those are actually kind of more dangerous right? Because comets go really really fast because they come from much further away so they have more time to like gather speed as they come towards the sun. There could be comments out there right now that take 500 years to go around the sun and we just haven't seen them yet. That would be bad news.