Elizabeth Meriwether's sitcom New Girl introduced Megan Fox’s Reagan Lucas for six episodes after Zooey Deschanel exited on maternity leave, but while she returned later on, she didn't stay forever — here is the Megan Fox New Girl exit explained. Reagan was popular among fans of the series and became a recurring character throughout season 6 when Nick rents out Jess' room while she's away on jury duty to pay for Schmidt's bachelor party. But considering the character was introduced as a filler for Deschanel’s Jess, her story arc was never intended to last long and, as a result, the Megan Fox New Girl run ended when season 6 wrapped.
https://screenrant.com/new-girl-megan-fox-reagan-season-6-exit-explained/