If I wear a cat ear headphone, am I going to look weird?

It depends on what kind of people you are hanging out with.

If you are concerned about being taken seriously i would be against it, but some people are too serious so there.

Yes you’ll look weird

I agree they look kinda cute but unless you're in a group of people who are also "dorks" or at least don't care enough to question it, you're probably not going to be taken very seriously.

It works if you're skilled enough: https://tvtropes.org/pmwiki/pmwiki.php/Main/BunnyEarsLawyer

You definitely will if you lack confidence.