Okay, so the sketch is in a courtroom with s judge, a prosecutor and four or five witches who are on trial for witchcraft. The witches need all to be dressed up in really obviously witchy clothes, or Harry Potter outfits or something like that. Despite the fact that they are obviously witches, they try to convince the judge that they are not witches, eg:

 

Prosecutor: So you're not witches, any of you?

 

The witches look at each other, noting the fact that they are dressed exactly like witches.

 

Witches: No, no, no!

 

Prosecutor: That's funny. You're dressed as witches.

 

Witch: Well, we were on our way to... a fancy dress party... yeah... for people who are ... not witches.

Prosecutor: So, what about that black cat then?

Witch: Cat? What - Oh, *this* cat!  He isn't our familiar or anything, if that's what you're implying, far too mean a cat for that, we're just going to use his entrails for our spe- (lls) *gets kicked by another witch* Spaghetti!  Perfectly ordinary spaghetti - would you like some?

Prosecutor: No, no, it's quite all right.  Now, I have an eye witness account that you *points at a particular witch* spent last Saturday night riding a broomstick-

Witch: *Interrupting* It's so hard to find decent strapping young lads.

Prosecutor: RIDING a broomstick across the sky, what do you have to say for yourself?

Witch:  Well, I think you should know, eyes are very fickle things, one minute they're in your socket, the next they're being strained for their jelly... *in a small voice* not that I would know anything about that...

 

i can't think of anything else, someone want to have a go?