Michael Shannon is a very talented, very intense actor who’s dominated scenes in everything from Boardwalk Empire to Man of Steel, but his powerful screen presence and ability to look incredibly menacing couldn’t save him from the might of a Porta Potty.

At a screening of 99 Homes this week, Shannon told Vulture that, while on the set of Batman v Superman: Dawn of Justice (we see him playing the corpse of his Man of Steel character, General Zod, in the trailer), he went into a Porta Potty in full costume and found himself unable to get back out.

“I was in my costume, and I couldn’t use my fingers because in the sequel I have flippers instead of hands,” Shannon said. “So I had these wax flippers on my fingers, and I couldn’t open the door, and I could hear Zack [Snyder, the director] being like, ‘Where’s Shannon? Where the fuck is he?’ and the whole crew was standing around. I was like, knocking on the door with my flippers, 'Let me out of here!'”

How Shannon was able to actually use the toilet without fingers is anyone’s guess, but at any rate, he was eventually saved by, of all people, the craft service guy.

“He was actually paying attention to what was going on. He came over and he opened the door for me. Otherwise I would have gotten fired.”

Apart from the humorous value of the anecdote, there’s actually some new Dawn of Justice information slipped into Shannon’s tale. Flippers? Zod doesn’t have flippers, unless Lex Luthor’s been doing some experimentation with his corpse to transform him into some kind of Kryptonian super-dolphin. Of course, Shannon wouldn’t go into any more detail about that, so we’ll just have to wait for more footage to figure out what’s really going on. For now, just take this important lesson from the story: Always be nice to the craft service guy.