The Paisley Poltergeist is a type of demon who infests clothing.
Paisley Poltergeists are invisible demons who infests the linings of clothes and patterns them. Their presence was known in the 1970s, though they are rare in the present. One appeared to menace Mr. Asquith's suit and the Ghostbusters took the suit for analysis.
Egon found out that the poltergeist's ecto-kinematic energy dissipates once it is removed from familiar surroundings. The poltergeist left the suit and infested the clothes of the other Ghostbusters, Janine and Slimer.