Lizzy Caplan is back in business with Sony TV and studio-based producer Jamie Tarses — she has signed on for a guest shot on their new ABC series Mr. Sunshine starring Matthew Perry. Caplan famously stepped in at the last minute to play a lead on the Sony/Tarses pilot for CBS Mad Love as a guest star and helped the pilot score a midseason order but she also caused a holdup in the deal as the network and the studio first tried to persuade her to stay on and then had to find a replacement when she declined. (Judy Greer was eventually cast in the role.) Mr. Sunshine stars Perry as Ben Donovan, the sports arena manager for the Sunshine Center, a second-tier arena in San Diego. Caplan will play a woman with whom Ben has a romantic interlude and then is surprised to see her showing up at work the next morning … as his boss’ (Allison Janney) new assistant. Caplan joins other recently booked guest stars on the show, including Nick Jonas, Jimmy Connors, James Taylor and Jorge Garcia. Caplan, who recently starred on Straz’s comedy Party Down, is developing a comedy at HBO with Will Ferrell and Adam McKay. The project, based on Julie Klausner’s memoir I Don’t Care About Your Band, which is eyed as a potential starring vehicle for Caplan.