Joker in the Pack

I bought a new pack of playing cards yesterday (they're rather nice ones with pictures of Monet's boats on the backs). I shuffled them well before playing patience with them, but of course I'd forgotten to remove the Jokers from the pack. so that game soon had to be abandoned. This got me thinking - why do we have Jokers in a pack of cards?

I understand the other cards - as they represent a typical Royal Court from the Middle Ages... and many of these courts had jesters which I suppose would be the origin of the Joker... but what purpose do they serve? For most games they are simply discarded (literally). So I did a bit of 'Googling' and found out that the Joker didn't actually turn up in playing card decks until about the mid 19th century when a particular variation of the game Euchre, which required an extra trump, became widely played in America.

The name 'Joker' was the name given to the Jack of Trumps in this variation of the game. The Joker eventually came to find roles in a number of popular games including Poker. As Poker spread across America and then to Europe, the Joker went with it and he was ushered into the court of the Royal Household. It was the Europeans that began to portray him in the form of the 'Court Jester' or 'Fool'. And that's why we find Jokers in packs of playing cards today.