VOY - Voyager is hit by an unknown energy wave that causes the crews memories and personalities to switch into the bodies of those nearest them.
Interesting. Has it occurred to you that "nearest" is not a reciprocal relationship? For example, where there are three people in a line, the minds on both ends would jump into the body in the middle, creating Tuvix-like situations in some bodies and a complete lack of consciousness in others. (Alternatively, the bodies on both ends get copies of the mind in the middle, while the body in the middle gets a mind from one of the ends.)