This tends to be visual based and all advice and comments are welcomed, but I especially like it because it still make me smile when I see anyone doing this and hopefully from now on, it will you too.

INT. OFFICE RECEPTION AREA – DAY

A motorcycle courier enters a company building and approaches the reception desk

COURIER
(inaudible through helmet....)

RECEPTIONIST
I’m sorry; I can’t understand what you are saying

At this point a second motorcycle courier approaches the desk with his helmet balanced up on his head and face clearly visible

COURIER 2
(clearly)
Afternoon, I’ve got a package here for Mr Anderson

RECEPTIONIST
OK, I’ll just give him a call and get him to come and sign for it

While the receptionist makes the call, the first courier notices how his fellow courier has his helmet placed and lifts his own helmet up in the same way, to reveal his face so that he can speak more clearly and addresses the receptionist a second time

COURIER
Sorry, what I was saying was that I’m here to pick up a parcel that needs delivering

RECEPTIONIST
OK, I’ll just go and get it for you

The first courier then looks at courier 2 and giving the thumbs up says

COURIER
That’s a good idea that mate, nice one

COURIER 2
Are you taking the piss?

Courier 2 then completely takes off his helmet to reveal he has a large, bulbous, dome-shaped head!

FADE OUT

As a variation on the theme, I also had a similar idea on the set of a video shoot for the Rap act MC Spanner and you see him lip-synching and dancing to his latest hit "You Can't Touch It ('Cos it's Spannertime)"

The direct shouts “Cut, cut, cut” and complains that he looks stupid in those enormous baggy pants and tells him to get them off while the onset stylish sorts him out a better looking pair.

So it cuts to a two person shot with the director and the stylish musing over various pairs until they find suitable ones and as they turn to hand them to Spanner to put on, he's standing there in his undies but his legs really are that huge shape.

Yeah that's funny. I wouldn't add a thing!

Very funny and I fully concur with Wildjesusfishkid. However, as I was reading this sketch, a thought that struck me was the equally preposterous idea of the second courier, also with visor down and speaking inaudibly through his helmet, meeting with the same response from the receptionist as the first courier. While she reacts accordingly to this frustrating and absurd situation, the two couriers strike up a muffled and inaudible conversation. The receptionist notices and is astounded that the couriers are having such a warm and amenable conversation.

It was good and well written. But I'm sure I've seen this joke done before with top hats and other large head wear.

I like the idea of courier 2 also being muffled but the secretary understanding him perfectly. A procession of other inaudible or uninteligible people (cowboy bandits with handkerchiefs over their mouths, fat people stuffing hamburgers into their mouths, a man speaking Spanish etc) all speak to the secretary but she understands them very well. It's a bit Airplane, but that's good enough for me.

Thanks for all of your comments and as always, some other good ideas come out of it once the original sketch was posted up. Another existing idea in mind was to have a dentist and patient scene and have a conversation where one voice in clear and the other muffled and the joke is that it's the dentist with the muffled voice, but it would have to be shot from the right angles and have the dialogue in voiceover style until the reveal at the end.

I personally don't worry too much if similar sketches have been done and I'm sure there must have been somewhere, but to me that's like saying you can only ever have one knock knock joke.

I actually got this idea from seeing someone with their motorbike helmet on and they put it up on their head while we were both in the queue at my bank. That gave me the odd shaped head thought as my final visual joke and then all I needed to do was work backwards and set up the situation with the other courier and receptionist.

Nice short and funny sketch - I also like the suggestions from Baumski and Scott. I think all 3 work and dont think a choice needs to be made between them - all 3 could be filmed as a small series (perhaps even more) as they are all funny in their own right.
It reminded me of an idea I once had when I saw a young girl with one of those bulky jackets - you know the ones - black with padded rings all around it, looks a bit Michelin-manish. I envisaged her taking it off and her body was the exact same shape.