Hillel Slovak , Flea , and Jack Irons were members of both bands , but Slovak and Irons left after Red Hot Chili Peppers ' first album . Original Red Hot Chili Peppers members Hillel Slovak and Jack Irons left that band just prior to it receiving its first record contract , preferring to focus on What Is This ? . Slovak rejoined the Chili Peppers for their second album and Irons for their third album .