1. To begin, all of the actors on Parks and Recreation improvised their “drunk off Snake Juice” reactions. This scene was directed by Amy Poehler, who attempted to create her giggle.
2. Chris Pratt improvised Andy’s line about typing Leslie’s flu symptoms into the computer on Parks and Recreation.
3. On Game of Thrones, Tormund stares longingly at Brienne and then smiles at her as they leave. Castle Black is not a scripted show.
4. When Randall and William visit Memphis on This Is Us, the scene in the barbershop is unscripted — Sterling K. Brown and Ron Cephas Jones discussed their real-life first haircuts.
5. While improv is heavily used in preproduction on Veep, one incident during filming involved Gary and Mike breaking an expensive tea set in London.
7. On Riverdale, KJ Apa broke his hand while pretending to punch through the ice to save Cheryl from drowning in the Sweetwater River.
8. Craig T. Nelson and Mae Whitman improvised the entire scene where Zeek takes Amber to see her wrecked car following her horrific car accident on Parenthood.
9. Will Smith improvised his speech about his father not wanting him on The Fresh Prince of Bel-Air.
10. During the episode “Gay Witch Hunt” of The Office, Steve Carell surprised Oscar Nunez by kissing him on the lips. According to the script, Michael was going to kiss Oscar on the cheek.
11. On Arrow, Stephen Amell improvises when Oliver takes off Felicity’s glasses in the scene where they have their first sex.
12. Jason Segel didn’t know Marshall’s father would die until they filmed the episode on How I Met Your Mother, so the final cut includes his genuine reaction.
13. Seth Green and Alyson Hannigan improvised the adorable scene where Oz and Willow joke about animal crackers on Buffy the Vampire Slayer.
14. When Daryl sees Carol dressed in her mother’s outfit in Alexandria, Norman Reedus improvised the line “You look ridiculous.”
15. Jensen Ackles made Jared Padalecki laugh on camera when he screamed Dean’s classic “son of a bitch” line on Supernatural. The line wasn’t originally written in the plot.
16. Iain De Caestecker mentioned Breaking Bad during the Season 2 finale of Agents of S.H.I.E.L.D when he uttered Jesse’s iconic catchphrase.
17. The entire scene in which Alison and Donnie buried a body in their garage on Orphan Black was unscripted. The director set up a camera and gave Tatiana Maslany and Kristian Bruun carte blanche.
18. In some episodes of Scrubs, Neil Flynn improvised his lines as Janitor. The script would read, “Whatever Neil says.”
19. On Breaking Bad, when Walter White kidnaps Holly in the famous “Ozymandias” episode, the baby says “Mama, mama,” completely unscripted.
20. On Sherlock, Benedict Cumberbatch forgot one of his lines while filming a scene in which Watson and Sherlock get drunk, but it worked, and Cumberbatch’s improvised line made it into the final cut.