S8, E15: Monica playfully prepares a special Valentine's Day for Chandler, complete with sexy lingerie and racy entertainment. However, Chandler is too shocked to respond favorably after accidentally viewing the wrong videotape: a birthing video meant for Rachel. Meanwhile, Ross has difficulty informing his girlfriend, Mona (recurring guest star Bonnie Somerville), that Rachel has moved in with him. His scheme to gain Mona's favor with a perfect Valentine's Day date is thwarted when Mona arrives at his apartment unannounced. Also, Phoebe tries to enliven a depressed Joey by bringing him the world's most cheerful dog. (Original Broadcast: Season 8, Episode 15)