‘Glee’ Goes Batman: Which Star Is Channeling His Inner Robin? (PHOTOS)

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Who let Robin out of his cage?

Glee showrunner Ryan Murphy snapped a photo of one of his cast members sporting the famed superhero sidekick’s costume on the set of his hit musical series.

“Who is that masked man keeping crime away from the halls of McKinley?” Murphy tweeted.

The actor, who joined the cast in 2010, was totally game as he courageously posed for a photo in his green tights.

So who’s the masked viligante?

Click through the gallery above for the big reveal…

In case you couldn’t figure it out from Blaine, erm, Robin’s adorable bow tie, it’s Darren Criss.

While both Criss and Murphy remained mum on when the Boy Wonder will be making an appearance on the show, fans suspect that the cast is currently filming scenes for Glee’s upcoming Halloween episode.

The fourth season of Glee kicks off Sept. 13 at 9 PM on FOX.