Series 3, episode 4, "The Speech". Sadly, it's also the episode where they convince Jen a box with a flashing red light is the Internet, but it has a subplot where Reynholm un-knowingly dates a trans woman. He finds her stereotypically masculine behavior attractive until he finds out she is transgender and a physical fight erupts between them.

It's not even on the upper end of offensive comedy about trans people, but when the episode was criticized, Linehan doubled down and has kept doubling down harder for 20 straight years, to the point where he now spends all of his time harassing, dead naming and doxing trans women on Twitter. His wife left him, writing jobs dried up, he's just a miserable has-been Twitter checkmark asshole now.

https://screenrant.com/it-crowd-controversy-graham-linehan-april-transphobic-bad/