The only funny instance of this was when Harry Enfield dressed up as Deborah Meaden from Dragon's Den.
What's this? Chip-shop psychology?All men do.
You do realise that half of the "comedians" that dress up as women are gay. Then there is the fact that a hell of a lot of them aren't even funny (Little Britain? I mean WTF, I'd rather pull my eyes out with rusty teaspoons than watch that tripe).
There is always the odd exception to the rule (Steve Coogan for one) that gets away with it.
Eddie Izzard is also straight, very funny also only just found out about him.