[quote=@MULTI_MEDIA_MAN]
Do...do I wanna know?
[/quote]

One of the characters in the show broke what is known as the Warp Barrier. Up until that point achieving speeds past Warp 9.99 was impossible. Tom Paris managed to achieve Warp 10 but because of some writing bullshit this caused him to begin to mutate/evolve/deevolve at an extreme rate. He went insane, kidnapped the captain of the ship and took her in the Warp 10 ship. When they were found both had mutated into lizards and may or may not have created a new species through breeding. They were taken back to the ship and the process was reversed.

It was about a hundred times more fucked up then it sounds.