Which episode was it when...?

There's a scene you remember from an episode but you can't figure out what episode it was? You've seen a screencap from a certain episode that you've never seen before? There's a quote you've never heard in an episode before? We may be able to clear it up for you!

Okay. There's one scene I've heard of but never seen. It's Chandler impersonating Richard with his finger as Richard's 'stache. I've seen it mentioned on tumblr, and it's also mentioned in my Friends Trivia board game. I've never seen the scene before. Is it actually real? And if so, what episode is it from?

I wanna know about it too!

I'll look. Shouldn't be too hard to find.

Any news on that?

Tbh I don't remember seeing the scene either but I'll do my research. Are there any more details about the scene or that's all you know/all you read?

Oh, right! I actually couldn't find it. Is there a particular line from that scene or a scene before? Was it after Monica and Richard broke up (as in, when you picture it, does Rachel have her S1-S2 hair)?

If I have either of those details, I could find it. I have a knack of deducing episode titles from a single line in the script (even paraphrased is fine).