The top pick of the pile has to be the only episode in which a Batman actor appears — Season 9’s “The Celebration Experimentation,” which features the late Adam West. Mr. West appeared as himself at Sheldon’s birthday party.
Sheldon has long been reluctant to celebrate his natal day due to a mean trick his twin, Missy, pulled on him when they were six. Amy hopes to reverse the trend by delivering on Missy’s long-ago lie; she plans on inviting Adam West to show up and act as a guest at Sheldon’s party. West does indeed truck over to the party — though he expects Amy to pay him — and the fete fills up with familiar old faces, like Sara Gilbert’s Leslie Winkle and Wil Wheaton, playing himself as a terrible evildoer. But this grand show of kindness causes Sheldon to have a panic attack, and only Penny can help talk him down.
This served as the show’s 200th episode, and it definitely shows, as lots of familiar characters got to return. After years of portraying himself on “Family Guy,” West was by this point an old hat at parodying his outré public persona, and this guest-starring turn here is no exception to the rule. Whether he’s forgetting Sheldon’s name, complaining that he wants to be taken home, or opining about the most overrated Batman, he’s a delight in a sea of guest stars, making this the most necessary “Batman”-related episode of “The Big Bang Theory.”