Plot

As Leonard and Penny attempt to hold another wedding ceremony everyone can attend, they have to deal with Penny's family arriving and Leonard's father spending the night with Sheldon's mother.

It's the day of Leonard and Penny's formal wedding ceremony, but things have the potential to go horribly wrong because of all the interrelationships between the attendees. Beverly and Mary, and Beverly and Alfred already have issues with each other and thus want to spend as little time with the other as possible. Beverly is threatening not to show as she feels humiliated on the assumption that Alfred and Mary slept together. Sheldon is angry at Alfred for supposedly defiling his mother. Leonard is angry at Sheldon for hating Alfred for supposedly defiling Mary. Penny's mother Susan is angry at Penny for divulging their family's dirty secrets to Leonard. Susan is also angry at Penny's brother Randall for his drug conviction leading to Susan believing Leonard's family will believe they white trash. Susan and Wyatt are not seeing eye to eye on how they should approach either Leonard's family or the wedding. As the ceremony approaches, the unpredictability of the situation may prove to be interesting. Meanwhile, both Howard and Raj are paranoid that the government is after them, all stemming from Howard's guidance system. Their paranoia is ratcheted up a notch when the military in the form of Colonel Richard Williams wants to meet with Howard but won't say exactly why.—Huggo

Leonard (Johnny Galecki) and Penny (Kaley Cuoco) are sleeping in bed when Sheldon (Jim Parsons) calls through the wall that they could be brothers. Sheldon also wonders if Leonard's father is currently doing despicable things to my mother. Penny reassures him that they are old and would be finished by 9:30.

As Penny is leaving to pick her family up at the airport, she stands at the door telling everyone not to bring up last night in front of Beverly and play dumb. Beverly (Christine Baranski) steps up behind while Sheldon comments Penny was showing them an example on how to play dumb. Penny is embarrassed and tries to leave. Beverly stops her, thanks her for going through all the trouble to have the ceremony, but she cannot attend because Alfred (Judd Hirsch) is going out of his way to humiliate her by parading around with some Bible-thumping bumpkin. Penny says that if she leaves, Alfred will know that he really got under her skin. Beverly will not stand for that.

Howard, Bernadette and Raj are having coffee in their kitchen. Raj thinks that the whole experience the previous night was funny. Howard denies it since he got a $500 traffic ticket. Raj answers the doorbell and finds Richard Williams (Dean Norris) of the United States' Air Force who wants to talk to Howard. A nervous Raj says that Howard is not at home. The officer won't explain what he wants, but leaves his business card asking Howard to call him.

Penny is driving her parents and brother to her apartment. Her mother Susan (Katey Sagal) is annoyed that they know about Randall's (Jack McBrayer) arrest and prison record. Wyatt (Keith Carradine) suddenly mentions the Walgreens they were passing. Susan doesn't want to discuss jail again. Wyatt adds, saying to Penny "Anyway, we're here, Slugger."

Howard is now worried that the Air Force knows where he lives. Bernadette adds that if he wants to live off the grid, he has to move out of his mother's house. Howard calls the phone number, greets the Colonel and sets up a meeting Thursday at work and the Colonel still will not discuss the purpose.

Leonard gives his mother a cup of tea and tells her how special it will be for Penny and him to share it with her. Mary and Alfred arrive at the guys' apartment. Sheldon then asks Alfred if he defiled his mother. Everyone is shocked. Alfred assures him that they only shared a cab and a conversation. Sheldon then asks if that conversation included the phrase "Your genitals are a joy to behold?" More shocking expressions occurred as Alfred remarks that neither he nor anyone has ever said that.

Penny's family has arrived at her apartment. Susan wants all the drug talk to stop and considers her family an embarrassment. Susan is worried that Leonard's parents are intellectuals and academics. She doesn't want them to think that they are white trash. Randall wonders what color "trash" she thinks they will believe.

Now back at the boys' apartment, Mary is asking how Sheldon could believe she would sleep with a man she just met. Sheldon points out that she'll do anything for unfamiliar men, like contributing towards building African churches for Jesus. Alfred says that he and Mary are planning on visiting each other. Alfred feels that she is a wonderful woman. Mary genuinely likes Leonard's father. Sheldon is angry since he is a mediocre academic and is sexual prowess is sub-par (according to Beverly). Leonard is insulted that his father isn't good enough for Sheldon's mother. Now everyone is complaining about who they have to stay with as Sheldon tries to diagram where who should be in which apartment.

Back in 4B, Wyatt asks his daughter about the world of pharmaceuticals. Susan doesn't want any more drug talk for the rest of their trip. Wyatt wants another beer while Susan thinks that he has had enough. Susan says that she can see why Randall turned up in jail. Leonard and Beverly enter the apartment and Susan is very glad to see him again and hugs him.

Back to 4A: Alfred tells Amy that he is sorry because of all the trouble he has caused. Amy is happy that Alfred and Mary like each other. Alfred reaches for Amy's hand and says, "You are a patient young woman." Sheldon growls and tells him to take a cold shower "Grandpa". She's mine!

Howard is still worried about what the Colonel wants and figures that it is bad news. They could do away with the invention and Howard is left with nothing. Raj tells a story about the scientists on the Manhattan Project who got nothing from it.

At Penny's, Beverly asks Randall what he does for a living. Susan steps in when he is between jobs. Randall adds that he is also between court appearances. Wyatt is happy to meet the woman who raised Leonard, this fine young man. Susan tells Wyatt that he doesn't need another beer. Penny comes in hoping that everyone is getting to know each other.

The wedding ceremony:

In a park setting backed-up with trellises, the guests are seated while Bernadette stands in front to officiate with Leonard. Amy has her harp. Stuart walks in and sits in the empty seat between Leonard's parents. Penny is escorted up the aisle by a very proud father. Wyatt welcomes Leonard to the family and advises him to not loan his brother-in-law any money. Bernie speaks that they are there to celebrate love. Not just the love between the bride and groom, but also for the love they have for them and between each other. Love is patient and doesn't put up with all the side-chatter coming from the audience's comments. Standing in front of all their family and friends brings up a lot of feelings in her, like eloping the first time was a good thing. Leonard has also made her very happy and she thanks him for marrying him. Leonard describes how as a scientist he has to explain why things happen and he can explain why someone like him ended up with someone like her. He doesn't have to understand it, just be grateful because he loves her. Alfred stands up and says to everyone even though he and Beverly don't bring out the best in each other, the best thing to come out of their relationship was Leonard. Before they can go on, Sheldon stands up and says he has to say something to a person who is pretty special. Amy starts to stand up and says, "It's happening!" thinking that she was getting a proposal. Sheldon then says "Leonard". Sheldon tells Leonard that he has always considered him family. Leonard and Penny thank him.

Leonard drives both his parents to the airport. They seem to be getting along until they start arguing about Leonard getting into the carpool lane. Amy is driving Mary to the airport with Sheldon in the back seat. Penny is driving her folks and brother to the airport. Her mother doesn't know what she was worried about since Penny's friends are just lovely. She does find Sheldon a bit peculiar. He reminds her father of a turkey they had that drowned looking up at the rain. Everybody has a laugh until Randall sees some cops and hides.

Title reference: Everyone assuming Mary and Alfred slept together.