The star did not feature in the reel of late actors, directors and producers during Sunday (4 March) night’s 90th Academy Awards, following his death from leukaemia last June.
While the segment usually honours those best known for their work in the film industry, Adam played Batman in the 1966 caped crusader movie, having risen to fame as the superhero in the 1960s TV series.
He also had roles in other films including ‘Robinson Crusoe on Mars’ and Three Stooges comedy ‘The Outlaws Is Coming’.
Many fans took to Twitter to voice their disappointment at the omission:
Some viewers also noticed the likes of RoboCop’s Miguel Ferrer, actress Dorothy Malone and ‘Texas Chain Saw Massacre’ director Tobe Hooper were also missing from the segment.
However, it is far from the first time Oscars bosses have made a gaffe in the In Memoriam reel.
Just last year, producers accidentally showed a photo of a living woman called Jan Chapman as they attempted to honour Janet Patterson - an Australian costume designer and four-time Oscar nominee.
Jan, a film producer, said she was “devastated” about the gaffe, especially as she was great friends with the late Janet.
In an email to Vanity Fair, she said: “Janet was a great beauty and four-time Oscar nominee and it is very disappointing that the error was not picked up.”
Last year also saw Patricia Arquette call out producers for omitting her sister Alexis from the reel.
She also told Vanity Fair: “It’s really unfortunate that the Oscars decided they couldn’t show a trans person who was such an important person in this community. Because.. it could have meant a lot to [trans youths].”