Man on the MoonGoofs
During his 1979 Carnegie Hall show ("Milk and cookies for everyone!") Andy presents an old movie clip and says, "We have with us the last surviving cowgirl from that 1931 film." However, the clip shown is from a 1942 movie, The Forest Rangers (1942).
During the scene where Tony Clifton is performing and Andy Kaufman walks out, making people believe that Kaufman and Clifton are two separate people, Clifton is played by Jim Carrey up to the point when Kaufman emerges from behind the curtain. Clifton is then portrayed by Paul Giamatti until Kaufman goes backstage, where Clifton is then played by Carrey again for the remainder of the scene.
Incorrectly regarded as goofs
Numerous anachronisms can be chalked up to artistic decisions; the film intentionally plays fast and loose with the timeline. For example, the Carnegie Hall performance was years before Andy Kaufman's cancer diagnosis; the title song wasn't written until after Andy's death; Andy didn't meet Lynne Margulies at a wrestling match; Stacy Carter hadn't met Jerry Lawler before Andy died (and certainly hadn't married him). Andy performs his imitation of President Jimmy Carter (elected 1976) before Saturday Night Live (1975) begins.
When Andy takes Lynne to the movies, he goes to the snack bar to get some popcorn. The Coca-Cola cups are of the 1990s, not like those of the time setting. In the late 1970s, Coca-Cola was simply called "Coca-Cola" or "Coke". The word 'classic' was not introduced until 1985, after the failure of New Coke.