"Castle" Season 6, Episode 21, titled "Law and Boarder," has revealed who is going to be the best man and maid of honour at Caskett's wedding. Beckett has asked Lanie to be her maid of honour, while Castle tells Ryan and Esposito that they can be his groom's men, as Alexis is going to be his best-man.

The episode also reveals that Lanie loves the dress that Beckett has picked for her. The two women discuss about the plan to go for the dress fitting. In the episode, when Ryan and Esposito find out that Lanie is the maid of honour, they wonder who Castle is going to pick as his best man. Unbeknownst to Castle, the two try to woo him. In a game of one-upmanship, Esposito fires the first shot when he gives Castle his favourite pen. Ryan hands Castle Jenny's secret shepherd pie recipe. Castle is surprised seeing that Ryan and Esposito are being extra sweet to him. He thinks they are weirdly sweet.

Thinking that Castle must be finding it difficult to decide who to pick between the two, Ryan and Esposito visit Lanie. Since she is the maid of honour, they ask her to decide on behalf of Castle. Lanie refuses to do that, saying that she is not Castle. After a couple of bickering sessions, the two men come to a conclusion.

Ryan and Esposito tell Castle that they understand his dilemma and thus have decided that they both would be his best-man. Castle reveals to the duo that he has already made the decision and has asked Alexis to be his best-man. He tells them that aside from Beckett, Alexis is the most important person in his life.

Ryan and Esposito did not see that coming. They cannot believe that they gave Castle their pen and secret family recipe in a bid to be his best man. Moreover, they are unable to digest that they got beaten by a girl.

When it comes to getting beaten by a girl, they were not the only ones. Beckett was continuously beating Castle in a game of scrabble. Castle was having sleepless nights because of losing to Beckett. Castle's losing streak came to a stop when Beckett came-up with the idea of strip-poker-game.