The offside rule was the subject for a brilliant Fast Show sketch in which John Thomson's clueless football "fan" character Roger Nouveau ("I'm not really that interested in England. They don't really stand much of a chance, do they? No, I think I'll give Germany my full support" etc) is having dinner with friends. I cannot recall any of the names (sorry!) but the conversation went something like this...

Roger Nouveau: ...and Wright just knocked it in! It was a fantastic goal, probably one of the best goals I've ever seen, but wait - the linesman ruled it offside! (laughs)
Woman #1: Oh yeah... listen, what is offside? Is that when the ball goes off at the side?
RN: (laughs) Off at the side? Off at the side? No, no; offside is, well, it's offside.
W#1: (is obviously none the wiser)
RN: Look, it's simple. Simple. (arranges salt and pepper pots on table) Offside. There has to be... a defender between the att... when the ball's kicked forward, there has to be a defender near the attacker, and... no, hang on, erm...

Fades out, and several sketches later...

RN: ...when the ball's kicked forward, the linesman rules offside when the ball is struck behind the halfway line.
Guy: That doesn't sound right...
RN: No, of course it doesn't sound right, because you're not listening properly. Look, it's simple. When the ball is kicked forward, there must be an attacker near the defender... Now let me... that... that's not right.

Fades out, and yet more sketches later...

RN: (still moving salt and pepper pots around) Let me explain this to you, in a way that you'll all understand, yeah? OK? There's the defender, there's the attacker, there's the goalie, and there's the ball. Now, he passes the ball to him...
W#1: I thought you knew all about football!
RN: (angry) I DO! (calms down a bit) When the ball is kicked forward, there must be an attacker between the defender.
Woman #2: Between the defender? Between the defender and what?
RN: Yes! Between! BETWEEN! It's a well known footballing phrase!
G: Between?!
RN: Yes!
G: A footballing phrase?
W#1: So what does it mean?
RN: AARGH! GOD! (throws the salt and pepper on the floor in a rage and leaps up) JUST FORGET ABOUT IT! YOU'RE NOT INTERESTED IN FOOTBALL! God, you're so detached from reality! (walks off and calms down a little)
RN: (sulkily) I'm going to clean my boots.