One dad's Christmas prank on his children backfired horribly after he dressed in a Grinch outfit in a viral video.

Cody Serrao was accused of "scarring" his two children for life after dressing up as the green monster and ripping their decorations from their home in Tyngsboro, Massachusetts.

A clip of the stunt was posted on Cody's Instagram account and quickly went viral.

It begins with a boy toddler and his older sister staring out the window just beside a lit-up Christmas tree.

A Grinch-figure dressed in a Santa costume then passes by the window and shoots a quick glance at the already whimpering youngsters.

Christmas Grinch prank
The Christmas prank backfired horribly

The kids turn to adult filming for help, who asks "why" before approaching the window and showing the two kids there's nothing there, asking them: "Where'd he go?"

As the man walks to the front door of the home, the whimpering of the two kids drowns out the background just as the man opens the front door, the Sun reports.

Pretending not to see the Grinch approaching the house, the man yells "Okay I thought I saw him but I don't see him anymore," just as the Grinch gets into full camera view.

Christmas Grinch prank
The evil Grinch approaches the lit-up Santa statue outside the home and attempts to steal him

The boy comes to the door and squeals and starts crying while pointing at the Grinch, and then responds in a deafening "yea" to to the man, who asked: "Is that him?"

Suddenly the evil Grinch approaches the lit-up Santa statue outside the home and attempts to steal him, prompting the man to say "no, not Santa. Don't take Santa," just as the Grinch unplugs the light and the boy is heard weeping behind him.

Christmas Grinch prank
The Grinch eventually took off his mask to reveal himself to be the kids' dad

As the Grinch approaches the front door, the camera pans to the two kids now fully howling and attempting to distance themselves from the green man.

Their wailing turns to sheer terror as the Grinch fastens his pace up the stairs with his arms outstretched in an attempt to grab the two children.

The Grinch picks up a Santa by the tree and inches closer to the children, now hysterically crying at the intruder.

But the film-taker then asks "who is it?" as the two kids continue screaming before the Grinch begins taking off his mask to reveal someone the kids recognise.

The startled little boy continued screaming even as the man gives the two tots a hug.

One Instagram user accused Serrao of "scarring his kids for life," while others described the prank as pure "evil".