Batman Easter Egg Found on Supergirl Set

A cool addition to Supergirl this year has been the inclusion of a National City dive bar where aliens can congregate in peace to meet, drink, and hook-up, both with friendly humans and with other extra-terrestrials.

It's a setting that production designer Tyler Harron said was originally intended to be a one-off, but which has taken up permanent residency on the show's set in Vancouver as writers have decided they liked it as a setting for the J'Onn J'onzz/M'gann M'orzz storyline.

The set is intended to look grimy and industrial -- and wow, does it, especially up close -- and, perhaps becuase it was done for a one-off, there are elements of it you might recognize from other shows (more on that later).

"I've been in places like this, so it was really important to me to get a really nasty texture, and dirty feel," Harron laughed. "The tables I wanted to be a little bit bashed and really dirty, to feel like there's gum underneath -- there isn't, but to give it that feel like you don't want to touch anything here. You might catch something, or something might catch you."

Besides a commitment to filth, Harron talked about creating little touches that surprised even executive producers Andrew Kreisberg and Greg Berlanti.

One such little touch is pretty surprising: there's an Easter egg that references Tim Burton's 1989 Batman movie in the entryway leading into the bar.

"Have you ever danced with the devil in the pale moonlight?" asks a piece of Sharpie-written graffiti on the hallway wall.

It's likely something that nobody could actually see on screen and so it serves primarily as a gag for those on set who might be waiting on a shot, or performing as an extra in the hallway, and trying to suss out what that awful handwriting means.

If you're not familiar with it, "Have you ever danced with the devi lin the pale moonlight?" is what Jack Nicholson's Jack Napier asks of his victims immediately before killing them in 1989's Batman.

It's the thing that ties The Joker back to Jack and allows Batman to realize that by defeating the Clown Prince of Crime, he's also bringing his parents' killer to justice.

Another piece of graffiti in the same handwriting offered a tantalizing hint that "Darkseid is coming" for Supergirl, but again we'll stress that it's unlikely the graffiti is an actual story tease and more likely it's just background gags.

Supergirl airs on Monday nights at 8 p.m. ET/PT on The CW.