Amy wants to throw Sheldon a birthday party because of what he did for her on her birthday in "The Opening Night Excitation" (S9E11) and because his birthday has never been celebrated, but Sheldon is scared
Sheldon tells Leonard, Penny and Amy that Sheldon doesn't celebrate his birthday because when he was a child, he had terrible birthdays. Anyone Sheldon invited would never come because they didn't like him, but it wasn't quite a problem because he didn't like them, either. But the real problem is his twin sister: For the whole day, Sheldon was tortured by his sister and her friends, but they went too far on their 6th birthday when the girls tricked Sheldon into believing that Batman was coming to the party. He waited by the door for hours and the closest thing he saw to Batman was when a robin flew into the window. And after that, he didn't want another party.
Everyone decides to make it as good as possible. Due to having had encounters with celebrities, Stuart tells the guys that he had met Adam West who played Batman. He gives them West's contact information and they pick him up and bring him to the party.
Apart from Leonard, Penny, Amy, Howard, Raj, Bernadette, Stuart and Adam West being the guests at the party, other guests included Wil Wheaton, Beverly Hofstadter, Barry Kripke and Leslie Winkle. Stephen Hawking, who couldn't turn up, attended via a laptop being held by Amy.
When Sheldon entered the room, he got a little scared and ran off to hide in the bathroom, but Penny went to talk to him. After they came back out, everyone gave Sheldon speeches and later celebrated with cake.
- Sheldon's birthday was a defacto celebration of the TBBT milestone.
- Sara Gilbert makes her first appearance on the show as Leslie Winkle in nearly six years, having not been seen or even mentioned since the third season finale "The Lunar Excitation" (S3E23), a span of 137 episodes. This also marks the first time that she appears in an episode with cast members Melissa Rauch and Kevin Sussman.
- First time Beverly was seen in the same room with Howard and Raj since "The Maternal Congruence" (S3E11).
- During the party, some things happened for the first time ever that had never happened before this event:
- All of Sheldon's living family, excluding his father (George Cooper. Sr.) who is dead, mother (Mary Cooper), brother (George Cooper. Jr.), sister (Missy Cooper), brother-in-law, nephew and grandmother (Constance aka Meemaw) are all absent from the party.
- As of this episode, Bernadette and Stuart still haven't met Sheldon's mother since Season 8's "The Maternal Combustion" (S8E23).
- Also, as of this episode, Bernadette still hasn't met Sheldon's mother since her absent appearances in Season's 4's "The Zazzy Substitution" (S4E3) and Season 5's "The Rhinitis Revelation" (S5E6).
- Plus: as of this episode, Bernadette, Raj, Stuart, and Howard still haven't met Meemaw since "The Meemaw Materialization" (S9E14) to which was an episode Stuart was absent from.
- Lastly, as of this episode, Amy still hasn't interacted with Sheldon's mother again since Season 8's "The Maternal Combustion" (S8E23) and Season 5's "The Rhinitis Revelation" (S5E6) since her only time of meeting her in Season 4's "The Zazzy Substitution" (S4E3).
- Laurie Metcalf (Sheldon's mother) and June Squibb (Meemaw) were not available to guest appear in the party scenes during this episode.
- Courtney Henggeler only played Missy Cooper (Sheldon's twin sister) once since in Season 1's "The Porkchop Indeterminacy" (S1E15). Also, in "The Cooper Extraction" (S7E11), Missy was heard screaming, but it is unknown if that was Henggeler's voice.
- All main characters of the show up to this episode, current and former were at the party, except Emily, unfortunately (as Raj had broken up with her earlier on).
- Bernadette doesn't get a chance to interact with Wil Wheaton at the party.