Jared Gilmore, 11, who played Don Draper (Jon Hamm) and Betty Francis' (January Jones) son Bobby on Mad Men, is leaving the show for a starring role on the new ABC 60 minute drama Once Upon a Time, and during an interview with TV Guide, he offered advice to his replacement, who has not yet been cast. "Be careful around January (Jones)," he warned. "She's not as approachable as the others. She's really serious about what she does. Everyone else is so nice." Gilmore is the third actor to play Bobby on Mad Men. His new series, which also stars Ginnifer Goodwin, debuts October 23rd.