Judith is pregnant, Alan believes he is the father, and Judith tries to keep him away from Herb. Meanwhile, Charlie tries to figure out why Jake is so irritable.
After his family acts mean-spirited during Alan's "surprise" birthday party, Alan decides he's had enough and moves in with his girlfriend and her mom.
Charlie needs Alan and Jake's help getting rid of the drunk, half-naked bimbo passed out in his bed when his girlfriend tells him she's coming home early from a funeral.
Charlie is so desperate to get Chelsea to return his accidental "I love you" and not lose control in the relationship that he is willing to propose to her just to make her say it.
Chelsea is jealous when Charlie's ex fiancée, Mia, calls him--perhaps rightfully so. Meanwhile, Judith goes into labor, Herb is incapacitated, and Alan runs into his ex-girlfriend and receptionist at the hospital.
Chelsea encourages Charlie to help his ex-fiancée Mia launch her music career, but does he still have feelings for her? And what if she's a terrible singer? Meanwhile, Alan wants Charlie to let Melissa move in with him.
Alan is forced to take care of Judith's baby when Judith's mom falls off the wagon, and Jake tries to blackmail Charlie when he runs over Chelsea's cat.
Jake refuses to stay with Charlie and Alan after they embarrass him in public, so Alan tries to convince Charlie to work together to settle their differences and stop fighting with each other.
Charlie invites Chelsea's sexy friend to stay at his place while she gets over a breakup, secretly hoping that he will get a chance to have kinky three-way sex.