'The Masked Singer' Hydra Costume Head Sawed-Off During Penn & Teller Reveal

No magic tricks necessary for Penn & Teller's big unmasking moment on "The Masked Singer" -- instead, it was a laborious process full of panic and mayhem!!!

Our sources say when the legendary comedy duo was revealed as the celebs inside the Hydra costume, stagehands had an issue deconstructing the costume at the moment of truth.

We're told it was a chaotic scene backstage, with folks scrambling to figure out what to do, and in the end ... the costume department made a very last-minute decision to completely cut off the middle head of the three-headed costume.

Our sources say the head was literally sawed-off ... and it basically ruined the costume.

Besides hacking off the head, we're told the costume department accidentally sliced a wire cutting off all the electricity used for Hydra ... making the eyeballs that once lit up completely useless.

Now, all this drama mostly played out off-screen when Penn & Teller were revealed earlier this season -- and our sources say producers panicked when they saw the head being sliced off. Despite the big reveal, they still had more filming to do with the costume -- like reshoots, promos and cutaway camera angles.

Fortunately, the wardrobe department's really handy with superglue -- we're told they meticulously pieced together Hydra's head, and it actually worked!!!