Wait, in 1976, there was a film called "Alice in Wonderland" directed by Gene Wilder. He co-wrote and starred in it with Jerry Lewis as the Mad Hatter. But Wilder's Alice was for all ages, not X-rated. So that's not it. Then there's the 1976 version directed by Martin Rosen, which is an animated film, again family-friendly. So perhaps the user is referring to a different version.
Another angle: the X rating might not be official. Sometimes, films are labeled X for their mature themes or for the times. In the 1970s, certain films might have been considered risqué but not necessarily officially X-rated today. Let me search for 1976 films, X-rated, Alice in Wonderland. alice in wonderland an x rated musical fantasy 1976 full
Alternatively, maybe this is a film that was never released publicly and is considered a lost film. Or perhaps it's a home video production. The user might be thinking of a VHS title from the 70s/80s that was X-rated, which is rare. However, I need to find if such a film exists. Wait, in 1976, there was a film called