Corporelectroscopy

 was the process by which two (or more) people switched their minds into each others' bodies.

The Javaman, a scientist with considerable imagination, called corporelectroscopy a "scientific implausibility". He was unaware that the theta-waves emitted by his Dorganator had caused the process to occur with the Sixth Doctor and Peri Brown.

The Doctor told Peri that corporelectroscopy was dangerous knowledge, and that it was "best left to the Time Lords". (PROSE: Turnabout is Fair Play)