Is it really ok to do that in comics? Are there no copyright violations of things like that?

For example if you have a scene with someone driving in the car and he turns on the radio. Then theres "let the bodies hit the floor by Drowning Pool" Of course you HAVE TO make a reference to an existing song if you do that.



Or maybe if you have a scene where a character is reading webcomics? For instance:
(*1st panel: show a computer screen with screenshots from 'PENIS' (that webcomic) on it*)
(*2nd panel: show a group of dudes reading it*)

But then again, "PENIS" is made by ANOTHER AUTHOR and not me. Does that get me copyright issues?

I've been doing that forever and never got in trouble.

I mean, to be safe, you could mention who made the song and stuff, but for the most part... not really.

References to music, TV shows, video games, etc:

No way you'd get into trouble. I'm sure that has to fall under the Fair Use act. You're just writing 1 or 2 lines of lyrics, it's not really the music. Maybe if you're Marvel you need to worry. But a webcomic? No.