The root of Cats’ muddied visual effects, it turns out, might have been more than just a time-crunched production. Director Tom Hooper, a source alleges, had no idea what an animated production entails—and he made life hell for the visual effects artists struggling until the bitter end to figure out what he wanted.

Cats was already halfway complete when the buttholes first showed themselves, a source who worked on the film’s visual effects recalled in a recent interview: “When we were looking at the playbacks, we were like, ‘What the hell? You guys see that?!’”

“We paused it,” the source said. “We went to call our supervisor, and we’re like, ‘There’s a fucking asshole in there! There’s buttholes!’ It wasn’t prominent but you saw it… And you [were] just like, ‘What the hell is that?… There’s a fucking butthole in there.’ It wasn’t in your face—but at the same time, too, if you’re looking, you’ll see it.”