The “world’s funniest joke” was exhaustively researched by Professor Richard Wiseman of the University of Hertfordshire. The reason for the research was to discover the joke that had the widest appeal amongst different cultures, demographics and countries. The project to find this joke was called the LaughLab, and encompassed 40,000 jokes and 1.5 million ratings. 
Here’s the joke:
Two hunters are out in the woods when one of them collapses. He doesn’t seem to be breathing and his eyes are glazed. The other guy whips out his phone and calls the emergency services. He gasps, “My friend is dead! What can I do?” The operator says “Calm down. I can help. First, let’s make sure he’s dead.” There is a silence, then a gunshot is heard. Back on the phone, the guy says “OK, now what?”
Why funny is funny
Many of the other jokes (I’ll share them with you in a moment) received higher ratings, but the one above had the most universal appeal.
We find jokes funny for primarily three reasons:
1. They can make us feel superior to others
2. They can reduce the fear of anxiety-provoking events
3. They can surprise us because of some kind of incongruity
The hunters joke contains all three – we feel superior to the stupid hunter, realise the incongruity of him misunderstanding the operator and the joke helps us to laugh about our concerns about our own mortality. 
The LaughLab found major differences in “funniness” between different countries and hence cultures. For example, people in the UK and Australia liked word plays such as:
Patient: “Doctor, I’ve got a strawberry stuck up my bum.”
Doctor: “I’ve got some cream for that.”
People from France, Denmark and Belgium, liked jokes that were somewhat surreal (I love this one too):
An Alsatian went to a telegram office, took out a blank form and wrote:
“Woof. Woof. Woof. Woof. Woof. Woof. Woof. Woof. Woof.”
The clerk examined the paper and politely told the dog: “There are only nine words here. You could send another ‘Woof’ for the same price.”
“But,” the dog replied, “that would make no sense at all.”
When you have to be joking in advertising
There is a plethora of research conducted on humour and its use in advertising, but lest we forget: advertising is neither science nor art – advertising is persuasion. People still speak of music as the universal language, yet there is a large divide between cultures – the halftones of Eastern music still feels somewhat eerie to the Western ear. We are not all the same when it comes to music and we are not all the same when it comes to humour.
There is humour in a relatively large proportion of advertising. Obviously, if its use is inappropriate, it detracts from the message and does not reinforce the intended communication. But with so many messages bombarding us every day, advertisers have to resort to some emotional tug just to get your attention.
The downside of humour is that funny ads are seen as less credible and not always relevant. 
The upside is that that humour (in the form of a one-line joke) can promote message comprehension.  However, you may perhaps have forgotten the brand that made the word ‘seerius’ part of our vocabulary (making that theory null and void). It was however a beautiful blend of using specific local culture to appeal to the masses. The campaign was for Polka (they were bought by MWeb, but the brand seems to have been discarded somewhere along the line).
I think the best jokes make you think for a second:
Two fish in a tank.
One turns to the other and says: “Do you know how to drive this?”
1. World’s funniest joke
2. Winning joke
3. Does humour make ads more effective? Millward Brown
4. Calvin P. Duncan, James E. Nelson, Nancy T. Frontczak. The effect of Humour on advertising comprehension. Advances in consumer research. Vol 11, 1984