Don't have a cow man - have some Simpsons collectibles instead

Today in 1997 the Simpsons' 167th episode aired making it the longest-running cartoon series ever

Still going strong in 2011, the Fox syndicated cartoon series about a dysfunctional (and yellow) family, The Simpsons became the longest running cartoon series of all time on February 9, 1997.

The show is an obvious candidate for the collectibles markets: it is well-known and much loved all over the world, and has generated a vast amount of memorabilia, both official and unofficial. Not all of it will gain in value of course, but rare and notable pieces will.

Animation artwork from Weekend at Burnsie's (Simpsons episode) (Click to enlarge)

It's easy to underestimate just how seriously the cartoon is taken too: just last August there was a great wave of activity on Twitter as the supposed 'future' date for Lisa's wedding day came and went.

There are already prolific collectors of Simpsons memorabilia. The Guinness Book of Records has credited an Australian, Cameron Gibbs of Victoria, with 2,580 items relating to the show. But unofficially, there are others who own far more.

The real record-holder should probably be Glynne Williams of Paul Fraser Collectibles' own home city of Bristol in the UK. He believes he owns 30,000 items of Simpsons memorabilia, though none of it is properly listed.

In particular, he has focused sections of autographs, car accessories, clocks and watches, figurines, foodstuffs and toys. Some are genuinely rare, such as a Radioactive Homer doll which was discontinued (ironically became the paint it is covered it is genuinely hazardous).

Still not married Lisa? Her wedding day has been and gone

Obviously the market for these collectibles is young one, and it's difficult to be certain how much some of the items will be worth in decades to come. Nevertheless, some pieces of Simpsons memorabilia have certainly proved to be genuinely valuable at auction.

For example original animation artwork for the episode Weekend at Burnsie's brought $2,509, and in general original celluloid from the series is expected to bring four-figure prices at Heritage and Bonhams.

Investors may wish to take a look at some original drawings of Lisa and Marge autographed by creator Matt Groening which are available right now.