From Worms Knowledge Base
The active worm chooses one of its teammates and becomes entangled with it. Thereafter in the turn, everything the active worm does, the entangled one will do or try to do, be it walking, jumping, or using a weapon or tool. For example, if the active worm walks left, the entangled worm will walk left, and if the latter meets a wall, it will stay there even if the active worm is still walking. In regard to weapons, if it is in unlimited supply, both will simply fire one, but for finite weapons, it will count as using both; for example, if there were three drills before the turn (say) and the active worm and entangled worm each use one, afterwards only one drill will remain, and if the active worm uses a super sheep (say) nothing will fly forth from the entangled worm.
There probably won't be many opportunities to use this quantum entanglement to your advantage, but situations could arise, for which it would be a fun utility to possess.