This is a sketch for the usual 'turn off your mobile phones' annoucement. Lights are down completely and numerous actors are planted amongst the audience.

Sound of phone ringing.
A1: (very loudly, on the phone): Hey, what's up? .... Yeah, I'm good how about you? ... No, no - I'm at the Science Revue .... Yeah, it's great, I've got this fantastic heckle ready to go - something classic like 'Your Mum'. .... yeah, I dunno why they haven't started yet ...
A2: Hey, SSSSSSSSSSSHHHH! Can you be quiet please?
A1: Hold on, wait, there's someone talking really loudly. I know, it's so rude!
A2: Hey, shut up!
A1: What - are you talking to me?
A2: You're such a douche! Be quiet!
A1: Sorry, I can't hear you, there's this guy yelling at me.
A3: BOTH OF YOU SHUT THE HELL UP!!
A2: Hey, no need to get aggressive.
(Another phone rings)
A4: Hello? Yeah great, how about you?
A3: Oh, serious?? Oh, hold on. (phone rings)
A5: Hey, I heard you were at the Science Revue?
A3: Yeah, I am - you too?! Hey, stand up so I can see you - I'm waving!
A5: Is that you? I dunno, it's really dark...
(more and more people join in answering phones and talking about random things. The audience will most probably start heckling at this point)
A6: I wish I'd bought some more jaffas.
A2: Twelve freakng dinosaurs! I said, don't you know how much they eat?
A1: Maybe Your Face would be funnier. What do you think?
ect. ect. (a loud phone ring on the voiceover to override everyone else)
V1: Hello?
V2: Listen, I just wanted to tell you you that you should turn your phone off when you're watching a show.
V1: Oh no, it's fine, they haven't had that mobile phone announcement yet.
V2: OK, but when they do, make sure you switch it right off, ok?
V1: OK.
V2: Oh, and before I hang up...
V1: ...yeah?
A1: Your face's mum! Hehehe...

Erm, lights down. More than before. Or perhaps up.