If I can imagine the Joker to have a lounge chair, then the Samoa by Mario Ferrarini would be his seat of choice. With a nice purple hue, metal frames under the the main structure cradle and suspend the seat. It also has an internal metal frame covered by shape-retaining polyurethane foam with differentiated density. It comes in non-removable cover and is available in fabric or leather. From Nube Italia.
Source: Daily Icon