Charlie must make a difficult decision about his future and with which woman he wants to spend his life: Chelsea or Mia

When Chelsea convinces Charlie to let Alan's new girlfriend, Melissa, move in, the girls end up taking over Charlie's house

Alan ends up playing maid to Judith's new baby as well as his former mother-in-law. Meanwhile, Jake uses an incriminating photo to blackmail Charlie

Alan starts working for Evelyn as Charlie works to fix the relationship between Chelsea and Jake

Jake stops at nothing to get away from Charlie and Alan, after they embarrass him out in public

Alan's advice to Chelsea that she get breast-reduction surgery is not met with enthusiasm by Charlie, who kicks him out, but staying with Evelyn has its own challenges

Alan and Charlie are shocked when they wake up next to a strange woman, and try to find out what happened

While overcoming a bad break-up, Chelsea invites her beautiful college roommate to stay at the house

While Alan struggles to cure his baldness, Charlie deals with the problem that he can't satisfy Chelsea

Chelsea wants Charlie to take dancing lessons for the wedding, when Charlie uncovers the truth that Chelsea has been lying about her finances

Jake is taught the art of infidelity by Charlie, while Celeste is away for Christmas

Jake hopes to win back Celeste by writing her love songs. Alan and Herb hope to keep Judith from finding out they've become friends

Charlie opts to have a colonoscopy in order to avoid going on a trip with Chelsea to see her parents. However, when he returns home, he finds her parents at his house

Charlie suspects Chelsea likes the lawyer representing Alan after his arrest for a bar fight

Chelsea and Charlie's relationship is at risk when Charlie's jealousy comes between them

Charlie runs off to Vegas and returns with a new wife, but she's not Chelsea

Charlie and Chelsea have a post-breakup one-night stand

Charlie has a return engagement with Chelsea's best friend, while Alan has an unexpected effect on a new female patient

Alan is torn between the bad influence of Jake's new friend and the hotness of his mother

Alan tries for an intimate night at a hotel with his new girlfriend, while Charlie takes a different approach to obtain the "girlfriend experience"

Charlie is visited by the ghosts of his ex-girlfriends while Alan and Jake are on a road trip

Charlie is miffed over Alan's planned attendance of Chelsea's birthday party and suffers the indignity of having Jake chauffer him around following a license suspension