Off the top of my head, SpongeBob SquarePants, Danny Phantom, Fairly Oddparents, The Big Bang Theory and It's Always Sunny in Philadelphia all have jokes, if not the main plot point of the episode, that are just mocking the existence of LGBTQ people.
I watched some of that during its original run, where did the transphobia come up? I’m sure I was just an idiot back then and didn’t notice
A lot of “that chick is a dude” type one-off jokes.