If a character is posessed, taken host, or has had their personality altered in some way so that they do not act normally, and the other characters work to return them to normal
Examples in Stargate SG-1, where Carter is host to Jolinar; Daniel has multiple personalities downloaded into his mind, etc.
In Sanctuary where Magnus contracts the under-sea parasite; Ashley is Brainwashed
In Stargate Atlantis where Wier and Sheppard are taken as hosts to the beings from the life-pods they found in space
I know there are more...
Do we have this one? I'm sure we do but i can't seem to find it