In the 6th season opener, Charlie runs into an ex-girlfriend and a child who bears a striking resemblance to Charlie.

Charlie borrowed money from Alan and on the day he is supposed to pay him back, Alan goes to ask Charlie for the money. He again finds Charlie in bed with a beautiful woman. After Charlie shoos him out and assures him he'll get the money for him later that day, the woman asks if Charlie is really out of cash and Charlie tells her not to worry, that he has plenty of hooker money.

Alan, Jake, and Charlie all decide to try new things: Alan is dating more than one woman, Charlie learns to cook, and Jake experiments with beer.

Alan is sure that things will turn bad when Charlie starts dating his receptionist.

Charlie tries to help Jake's former teacher, who became a stripper after dating him, but things go from bad to worse when she has a religious conversion.

When Judith kicks Herb to the curb, Alan comes knocking; Jake is sent to stay with a less-than-willing Charlie for three months during Judith's meltdown.

Alan tries to escape Judith's grasp as Charlie and Herb go on the prowl to pick up women. They later end up going back to Herb's hotel room with two prostitutes, where Herb declares his love for Judith and races over to win her back.

Charlie's new girlfriend Chelsea asks him to spend the night at her place, which puts Charlie well outside of his comfort zone, while Alan tries to enforce a punishment on Jake initiated by Judith for mooning a group of girls.

Charlie finds himself in an uncomfortable position when Jake takes off with the daughter of a former NFL player. Charlie's Mercedes proves a boon to Alan's love life.

Evelyn offers to pay for Jake's college education, and Alan becomes listless because he has no compelling reason to work anymore, while Jake discovers a hidden talent in the culinary arts that may allow him to bypass college altogether.

Charlie finds himself re-examining his wild ways when an old friend dies and begins to feel that his time on Earth may be drawing to a close.

Charlie and Jake fight for the affections of a waitress, while Alan fights sexual tension with his receptionist.

Judith is pregnant with a baby girl and Alan is convinced he is the father.

Melissa doesn't think Alan's family appreciates him, so she asks him to move in with her and her mom.

Charlie ends up in couples counseling.

Charlie has to remove a half-naked woman from his bedroom before Chelsea arrives.

Charlie's admission that he's in love with Chelsea gets a surprising reaction from her

Chelsea's illness gives Charlie a chance to prove he can take care of her, but also yearning to run away from the situation.

After Chelsea discovers a nude picture of another woman on Charlie's cell phone, he blows off steam by going out for a night of drinking with Alan, Herb and his neighbor.

Charlie's desperate to make sure Chelsea and Evelyn don't befriend each other following their first meeting.

Chelsea is asked by Alan to arrange a blind date between he and her new friend, unaware that her new friend is Rose.

Charlie mourns the loss of his bachelor pad as he reluctantly allows Chelsea to move in. Meanwhile, Alan discovers there is no longer much space left in the house for him.

Alan and Chelsea become best buds, and Charlie decides to take advantage of the situation.

Charlie starts to question his relationship with Chelsea when he hears that Mia is back in town. Meanwhile, Judith goes into labor and Charlie, Alan and Herb rush her to the hospital, on the sixth season finale.

Alan and Jake meet Walden Schmidt, a broken-hearted billionaire.

Walden deals with his ex-wife, Bridget.

Alan prepares Walden for a date with Bridget, while Jake decides to emulate Walden and drop out of school.

Walden goes looking for Mrs. Right while Alan has an opportunity to reconcile with Lyndsey.

Alan has trouble accepting Lyndsey's seedy movie past, and Walden tries to cheer him up by throwing a party.

Walden receives divorce papers from Bridget, but forgets his depression when he meets a girl who looks eerily like her.

Jake has a crush on his chemistry tutor, who has a crush on Walden. Meanwhile, Alan obsesses over the journal his brother left him in his will.

When Walden begins redecorating the beach house, Alan becomes overly emotional.

Upon his release from the hospital, Alan is met with a slew of challenges that test his ability to cope.

Walden hits it off with a British babe, but neither of them is sure he's ready to re-enter the dating world.

Walden is trying his best to impress his new love interest when Bridget reappears in his life.

Walden's mother arrives and Alan is smitten with her, even as she reveals a secret about Walden's past that sends him into a downward spiral.

Walden’s ex-wife and mother try to take control of his company, so he turns to Alan for help.

Zoey tries to convince Walden to cut his hair and shave; Alan and Lyndsey revive their relationship.

Walden tries to loosen Zooey up by sharing some of Berta's special brownies.

Strained relationships and girl-fighting result when a huge storm traps Walden, Alan, Zoey and Lyndsey in the house on Valentine's Day.

Walden and Zoey's relationship suffers after they share a near-death experience. Meanwhile, Alan wonders if Lyndsey has a drinking problem.

Walden's ex-business partner shows up at the beach house looking to make peace.

Alan and Lyndsey introduce their mothers. Jake and Eldridge get a ride from Walden to a party.

Walden breaks the news to Zoey that he is going into business with his ex-wife. Alan and Lyndsey try to cope with their mom's relationship.

Walden's commitment is tested when Zoey and her daughter come to live with him. Meanwhile, Alan gets more than he bargained for when he moves in with Lyndsey

Charlie's ghost pays a visit to Alan after he suffers a minor heart attack.

Alan is showered with love and affection upon returning from the hospital, but Zoey isn’t so sure it’s deserved.

Jake is pressured to make a decision about his future.

After a health scare on Halloween, Walden decides he needs to change his life.

Alan has second thoughts about getting married after he's asked to sign a pre-nup.

Alan and Walden have a meeting with an adoption social worker that hinges on them being convincing as a loving couple. Lyndsey returns after 60 days in rehab.

A birth mother considers having Walden and Alan adopt her baby.

Walden becomes a foster parent to a 6-year-old boy, but worries about himself when they don't hit it off like he hoped.

Alan breaks Walden's rules when he realizes that Louis thinks he's cool, and he wants it to stay that way.

Alan and Walden befriend three moms at a kids’ gym, but things get complicated when Walden becomes attracted to one of them. Alan goes out for a girls’ night with a group of moms.

Alan and Walden attempt to convince Louis that Santa Claus is real.

Walden discovers how challenging it is to be intimate with women when his foster son, Louis, is in the house. Also, Herb asks Alan if he can go on a date with Lyndsey.

Alan takes it upon himself to help Walden keep Louis after the social worker discovers he and Walden are not really a gay couple.

Walden joins a group for adoptive fathers, and finds it to be a nice escape from Alan.

When Alan breaks up with their social worker to get back together with Lyndsey, Walden worries it will affect Louis’ adoption.

Walden fears if he breaks up with Ms. McMartin, it will jeopardize his adoption of Louis. Also, Alan hesitates when Lyndsey asks him to move in with her.

After they sign their divorce papers, Walden offers Alan the gift of his choice, but when Alan chooses something selfish and impractical, it puts his relationship with Lyndsey on the line.

Charlie Harper is alive. Or is he?

Charlie Harper is alive. Or is he?