On its own, the holiday song "Carol of the Bells" already seems creepy, but it's even more weird when the turrets from Portal sing about murder in their version of the holiday classic.

A new video released by YouTuber Harry "Harry101UK" Callaghan aptly depicts the holiday song, as sung by the turrets, in all their weird and murderous glory.

Callaghan used Source Filmmaker to create the video. Source Filmmaker is an open source tool by Valve that lets anyone make movies using the Source game engine.

"Because the Source Filmmaker uses the same assets as a Source-engine game, what goes into the game can be used in the movie, and vice versa," writes Valve on its website. "By using the hardware rendering of a modern PC gaming machine, the SFM allows storytellers to work in a 'what you see is what you get' environment so that they can iterate in the context of what it will feel like for the final audience."

The results from using the tool are something like this:

Perhaps the best part of the video are the in-character lyrics sung by the turrets:

Time for some tests! Shoot the subjects!

Make them all die! If they survive! Bake them a pie! The time is nigh! Testing is here! Let out a cheer!

Please sing along! This is our song! For the Animal King! We'll always sing! Guns we will bring! Bullets we will sling! Fill them with holes! That is our goal! Test if you dare! Are you still there? Please sing along! This is our song!

With joyful ring! We're caroling! Neurotoxin! Is pumping in! From everywhere! Filling the air! Filling the air! Filling the air!

Oh, how they pound! Raising the sound! Throughout Aperture! GLaDOS is here!

Merry, merry, merry, merry science! Merry, merry, merry, merry science!

Testing all year! With Christmas cheer! We'll only stop! When subjects drop!

[Intermission]

With joyful ring! We're caroling! Neurotoxin! Is pumping in!

From everywhere! Filling the air! Filling the air! Filling the air! Oh, how they pound! Raising the sound! Throughout Aperture! GLaDOS is here!

Merry, merry, merry, merry science! Merry, merry, merry, merry science!

Testing all year! With Christmas cheer! We'll only break! For tasty cake!

[Turret Solo]

That is our song!

You'll never hear "Carol of the Bells" the same way again. You can also download the song on Bandcamp.

Merry Science, everyone!

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