The Enterprise-D shuttlecraft in which Worf returns from a bat'leth tournament in 2370, passes through a quantum fissure and begins sliding between parallel realities.
The Curie is the shuttlecraft at the centre of the Next Generation episode Parallels. Worf is flying it home from a bat'leth tournament on Forcas III when it crosses a quantum fissure, a point where many quantum realities meet, without his noticing anything unusual.
From then on he shifts from one reality to another whenever Geordi La Forge's visor is near him, finding himself married to Deanna Troi and serving under Captain Riker. Data eventually traces the cause back to the shuttle's flight path.
When the fissure ruptures and hundreds of thousands of Enterprises pour into one region of space, the crew locate the Curie that belongs to Worf's own reality. He pilots it back through the fissure with a modified warp field, sealing the breach and returning every ship to its proper universe.