FAQ for
Pink Flamingos (1972) More at IMDbPro »

Yes. Even though Divine is clearly seen eating actual dog feces in the film, some viewers find it hard to believe that what they're seeing is real. John Waters goes into detail about shooting the scene in his book "Shock Value", where he reveals that they had a terrible time following the dog around and waiting for it to "go". By the time the moment of truth arrived, Waters was losing daylight and was terrified that Divine wouldn't be able to go through with it.

By his own request, the "singing asshole"s name has remained secret. Presumably Waters' knows who it is but he's not talking.