The Big Bang Theory finale received praise for its lack of closure and a memorable cameo by Sarah Michelle Gellar. The writers, who were fans of Buffy The Vampire Slayer, saw an opportunity to have a celebrity appear alongside Raj in the finale. Chuck Lorre reached out to Gellar, who instantly agreed to the cameo because her family loved the show. The surprise appearance caught the cast, including Jim Parsons, off guard. During Sheldon's Nobel Prize speech, he sees Gellar in the audience next to Raj and genuinely reacts with confusion, saying, "Is that Buffy the vampire slayer?" The showrunners wanted to honor Gellar's real-life relationship with Freddie Prinze Jr.

When Jim Parsons announced he wouldn't return for Season 13, it meant the end of the show. The cast had an emotional final table read, especially during Sheldon's speech. Parsons felt a lot of pressure to get the finale right, as comedies often struggle with endings. However, he believed the show did the best job possible. He said, "It ended in the way that I hoped it would, in that it felt right." Parsons acknowledged that not everyone would love the finale, but he felt it wrapped up in the right way. Fans agreed that the show ended perfectly without a sense of closure, knowing that everything would be okay as the friends continued their lives.