The Parallels reference article from the English Wikipedia on 24-Apr-2004
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Parallels

On his way back from a Batleth tournament, Worf proudly boasts to his log that he won the Championship. Little does he know that he was just sucked into a space-time continuum phenomenon! When he arrives on the Enterprise, he cautiously enters his quarters...it's his birthday and he HATES surprise parties! After setting down his batleth and trophy, and taking a look around, he is quite confident that maybe he will get to spend the evening alone. Suddenly, the crew jumps out and turns on the lights! There is much rejoicing and celebration and grumbling(you know who). But weird things start to happen. The cake was chocolate, now it is yellow! Captain Picard is attending when Riker said he couldn't make it! Data's painting that Deanna had hung on the wall has now moved across the room!

Worf continues to experience all these changes, but no one seems to remember things ever being different! Finally, he convinces Deanna that he is certain some po'taH is going on. It turns out that Worf has a different signature than that of the universe, meaning that he is in the WRONG universe. Data explains that when Worf was returning from that Batleth tournament, he accidently entered a time-space fissure. The warps engines on his shuttle caused a reaction in the fissure sending Worf into quantum flux, through the endless possibilities of time and probability. And whenever Worf got close to Geordi, whose visor uses the same warp technology, he would get thrown into another universe.