Walden wakes up next to Zoe, with a smile. He retrieves a small, beribboned box from his bedside table, and tries to wake her , by shaking the box, shaking the bed, and finally by disappearing under the covers, which definitely brings her to life. Inside the box is a key to his house. Zoe says it is premature in their relationship. Seeing the time, she hops out of bed to go to pick up her daughter, and then her parents at the airport.

Walden asks why he can’t go with her to meet the parents. It’s Christmas, his mom is coming in as well, and he’d like them all to meet. Zoe feels that they are still just getting to know each other, but he disagrees.  He answers her “what color are my eyes?” question, correctly, and then adds a few other facts that show he’s been paying attention. But she’s adamant – no families this year.

In the beach house, Walden is trimming the tree, and Berta tells him that, although she did what she could, Jake’s room still has a teenage stink to it. He wonders if he should put his mom in Alan’s room instead, but Berta says that room smells of failure and foot powder. Noting Walden’s Santa hat with mistletoe attached, Berta asks for, and gets, a Christmas kiss. She asks him if he knew that they make belt buckles with mistletoe on them, and then tells him to check his stocking. He gives her a Christmas bonus of three weeks’ pay, and another kiss on the cheek, although she would have preferred he put on the mistletoe belt buckle.

While Walden speaks to his mom on the phone (she’s driving in from San Diego,) Alan is on another phone asking his mom if they should spend their first Christmas without Charlie together. She says she’d rather get laid, as would he. Meanwhile, Jake and a friend have concocted a way to fool both of their parents into thinking that their at the other parent’s house for Christmas.  

Like a kid, Walden happily talks about how great things are for him. Alan, on the other hand, is miserable. Alan recounts the holiday tradition he shared with Charlie; Charlie would drink a gallon of eggnog, and then try to throw him out of the house at gunpoint. Good times! 

Walden invites Alan to spend the holiday with he and his mother. He then mentions that Alan is about the same age as his mother; if they started dating, Alan would be his new daddy!

Walden’s mother, Robin, arrives, and Alan is immediately smitten. At dinner, Robin wonders if Alan is the woman Walden doesn’t want her to meet. She thinks a 33 year old man living with a 60 year old is a rather strange setup. Alan says he’s only 44. She says, “Right, me too” with a smile. Walden explains that Alan helped him through his breakup with Bridget, and then needed a place to say, so he asked him to stick around. She notes that he hasn’t changed. When he was a little boy, he’d bring home sick, helpless animals all the time.    

Alan asks Robin what she does for a living. She’s a primatologist, who works with gorillas. Alan quips that that makes her the ‘gorilla of my dreams.’ She maintains a gorilla sanctuary, where the apes can live a safe, stable life. Walden reminisces about his imaginary gorilla friend, Magilla, and is shocked to learn that Magilla was real, and raised with him from birth to the age of four, as an experiment. Robin shows Alan and Walden pictures of Walden’s youth with Magilla, and mentions that it was necessary to keep Magilla hidden from the Home Owner’s Association. When Walden went to pre-school, he was told that Magilla had been sent home to the jungle. Robin says they had no choice; Magilla was getting too big, and tried to kill a Jehovah’s Witness. Walden gets angrier and angrier as he recounts growing up, believing a gorilla was his brother, and constantly worrying that if he made one false move, he’d be sent to Zimbabwe. Robin is surprised that he’s so disturbed, and he says she didn’t notice because she was so busy doing her experiment. Walden storms out of the room. Alan asks Robin if she’s seeing anybody

In the living room, Robin tries to reach Walden, who has apparently left in a snit. She had no idea that he had repressed all of his childhood memories. Alan thinks he should reconsider the gift he was going to give Walden – a bathrobe covered in a Curious George monkey print. Alan then recounts a number of horrifying events from his own childhood, and says that as far as he’s concerned, Robin’s a candidate for Mother of The Year. She admits that she had his embryo frozen so that she and the mother gorilla would give birth at the same time, for scientific purposes. Alan asks her what she learned after all that time and energy. “My son is smarter than a gorilla.” she replies. Alan says that his is not.

Walden arrives at Zoe’s apartment, drunk and slurring. She says it isn’t a good time. He says it isn’t for him either; his mother is a mad scientist, and he spent the first four years of his life flinging poop with his brother, the gorilla.

He’s introduced to Zoe’s very proper British parents. He immediately asks Zoe’s mother Cheryl if she would raise her daughter with a wild beast to satisfy her scientific curiosity. She says she can’t say, but she has cross-bred orchids. With Zoe’s parents standing there, Walden says that he always strives to give Zoe multiple orgasms, in fear of being sent to Central Africa. Cheryl says that she and the Commander have often gone to Africa on safari, but she can’t say she’s had multiple orgasms.

Zoe calls to say that Walden is drunk, and has climbed on to her roof. Alan and Robin drive to the building, and Alan crawls on to the roof to talk to Walden. Walden is still angry with his mother, but Alan has a few horror stories of his own. Alan says neither of them can keep blaming their mothers for how their lives turned out. Alan admits that he’s never forgiven his mother, but he’s a small, petty man. Walden, on the other hand, has accomplished great things, and has the capacity to accomplish even more. What about Magilla, says Walden. “I loved him and she sent him away.”

Alan reminds him that he knows what it’s like to lose a brother, who also tried to kill a Jehovah’s Witness.  Suddenly a helicopter arrives, and Walden goes into full King Kong mode. A crowd has gathered below, and Zoe introduces herself to Robin. (They look rather alike, actually.) Zoe also introduces Robin to her parents, who behave in proper British form.  They note that Walden is a charming young man, but he thinks he’s the brother of a monkey.

On the sidewalk, Jake and his friend look up at the roof, while munching on pizza. Jake says he thinks that his dad up there on the roof, and then agrees to go get some frozen yogurt.

Robin takes Alan and Walden to the zoo, where Magilla and Walden have a joyful reconciliation. Alan notes that it’s the most beautiful thing he’s ever seen. He sees that Robin is carrying a tazer, and she admits that with a 400 pound gorilla, things could have gone either way.