No, it's not a joke, but an actual trick. Here's the description from Hank Lee's Hot List (www.magicfact.com
A bizarre new packet trick from Bob Farmer and Roy Walton - Mutanz!
Bob says it's inexplicable, unexplainable, enigmatic and just plain weird! A cascade of alchemical conundrums! A phantasmagoric orgy of cabalistic conjuration! A bewildering bafflement of uncanny dimensionality! Strange and supernatural forces twist and possess ordinary cards until they become grotesque mutants in the hands of the spectator!
But, that's just Bob talking.
I will tell you that Mutanz is one of the cleanest, most amazing, packet tricks I have ever seen. Four cards magically turn face up and face down in a manner so convincing and deceptive, it looks like trick photography. Your eyes will pop! But that's just a buildup to one of the most astonishing and surprising card vanishes of all time -- and it happens right in the spectator's hands.
And it's really quite easy to do. No angles. Everything examinable. Resets instantly. What more could you ask for? Comes complete with special Bicycle Poker Size Cards and full instructions. (30.829)