Has anyone ever noticed how, in most (if not all) classic sitcoms, walls supposed to be made of bricks or stones strangely wobble whenever someone slams a door or, sometimes, just lean on them, as if they were actually made, ridiculous thought, out of thin sheets of plywood? It's amazing, isn't it?

The most amazing thing is how they got away with that for some 20 years, or probably more...
I was just watching the first season of "Bless this House" recently, and there's almost one wobbling wall in every episode, it's just too funny, if Sid James wasn't enough on his own...

But if you keep your eyes peeled, I'm sure you could spot wobbling walls well into the 80s, at least, I remember some in "The Young Ones" for sure, and I'd guess it could still happen even in these modern and technologically developed days, it all depends on the budget, I shouldn't wonder

But the most "special" wobbling wall of them all must be that out of "Fawlty Towers", an outtake actually, which I'm sure owners of the DVD would have appreciated.
Basil had been sampling, or rather pretending to sample, walls by knocking on them to ascertain their sturdiness throughout the episode, so, when the script has Sybil slam a door rather literally in his face, and she does it a bit too overenthusiastically, thus making the fake wall wobble rather dangerously and actually threaten to fall on Basil, what John Cleese does, without losing a beat, nay, without batting an eyelid, is just sample-knock on the wall as he'd been doing all the time...
I've seen the recording, of course, but I can only imagine the faces of those who actually witnessed that in the audience, at the time, they MUST have fallen out of their seats...

That's sheer genius, if you ask me... if John had time to think, a couple of milliseconds perhaps, he'd obviously realize that the scene would have to be cut and reshot, which in fact it was, but he didn't, he had an audience to deal with, let's not forget, and he just reacted... and that was marvellous!
Funny how one of the greatest scenes in the history of comedy, to me at least, is not even "official", and relatively few people have actually ever seen it...

Well, I must admit I'm a bit partial towards John Cleese being the funniest man alive... if he only could take the bother of being actually funny again, inbetween sipping wine and ranting about football...
