Ho Yay: Ryan and Esposito. Oh so very much.
- In "Den of Thieves", the word 'partner' is used repeatedly in questionable context.
- Also in the same episode: "Where's Esposito? WHERE'S ESPOSITO?
- In "Lucky Stiff" Ryan reveals that he plays Esposito's lottery numbers, so it wouldn't be awkward if one of them won. Uhm yeah...
- Even moreso because Esposito's numbers are the dates of his firsts - as in, his first time in combat and the first time he had sex.
- Castle to Esposito about Ryan when Ryan's girlfriend calls him yet again.
Castle: Don't worry, he still loves you.
Beckett: When I'm not here, do you guys braid each other's hair and discuss who's your favourite Jonas brother?
Esposito: No... but it's Nick.
Ryan: Absolutely Nick.
- Esposito throwing Ryan up against a wall in "Knockout", after finding out that Captain Montgomery was involved in Johanna Beckett's murder. And the heads of a thousand Slash Fic writers exploded...
- It gets better in "Dance With Death", when a (keep in mind, married for seven episodes) Ryan pretty much insists Esposito wear his wedding ring when interviewing suspects at a strip club... to see if strippers will flirt with him even if he's not taken. The scene is set up to look like a proposal, which isn't even mentioning the subtext that Espo gets a date because of the ring... and later, can't take it off because his finger's too big and needs Beckett's hand cream. Ryan panicked. Slashers squealed.
- The best thing about the Ho Yay here is that Esposito and Ryan pretty much acknowledge the fact that it's there and just roll with it.
- Between Castle and his old high school friend Damian in "The Last Nail." Teenage boy sent off to a boarding school, gets homesick, and gets comforted by an older student.
- In "Probable Cause", Esposito assures Beckett that she's not alone in worrying over Castle's situation as the prime suspect of their current murder investigation.
Esposito: I know how you feel about the guy. I love him, too.
- In seasons 6's episode "A Murder is Forever", the victim of a week is a renown relationship therapist with a best-seller on relationships, and after having read it Ryan refers to it... but in the context of his relationship with Esposito, not his wife.
- In "Under Fire", with Ryan and Esposito trapped in a burning building and Ryan's wife going into labor, they manage to contact the crew, and Jenny asks her husband what to name the baby. His response for a boy's name is "Javier". Even Espo criticizes that choice. Luckily for both of them it's a girl.
- In the Season 4 blooper reel, Adam Baldwin grabs Nathan Fillion's butt. He responds by swatting his hand away and saying, "Later."
- Several seconds later, the two (almost) kiss.