From Worms Knowledge Base
When activated, the worm using this weapon performs mitosis, and splits cleanly into two worms. Health is halved, such that each clone have the same amount. This weapon does not end the turn for the original worm, who can continue as usual.
For avoiding a player cloning worms without a thought for his processor, this weapon can be used only if there are less than 8 worms in the team. Also, the worm which is cloned must have at least 2 health points, and if the number of health of the worm is odd, the health of the cloned worms will be the half of the health of the worms which is cloned minus one and the health of the non cloned worm would be the same as the health of the cloned worm plus one. The cloned worm would not leave a grave when it died, so it couldn´t be used to make infinite worms in a game using it in combination with the Resurrector.
If the worm happens to be in a tight spot where another worm simply could not exist without intersecting terrain somehow, then the clone should take the same position as the original worm, in the same way that worms generally overlap during games anyway.
If one worm was to die the remaining worm would carry on as usual. Also, the name of the cloned worm would be just be exactly the same as the worm which is cloned.
This weapon would be useful in those situations where you don't want to risk a (whole) worm, and splitting a powerful worm will give you a sort of back-up copy should things go horribly wrong. You may even want to use a kamikaze or suicide move without actually killing your worm, particularly useful on low health. Even better, doubling the number of worms will double the damage you can do in a suicide move, if you plan on killing both with a standard weapon, near an enemy worm.
Also useful for restricted maps where select worm is available (e.g. "Team17" games), as it enables you to position more worms around the map for greater coverage and strategical freedom. Without select worm though, this weapon could turn out to be more a hindrance.
Cloning is one of those other controversial topical subjects of the modern world, so bringing that into Worms with a comical, over-simplified animation would be welcome, and it could be accompanied by that 'blub' sound-effect you're most likely to associate with a blob of microscopic jelly falling down the stairs.
PS, cf. the proposal of Fusion.