Came across this video a week ago on Youtube. Sometimes, the UK version of CN got very lucky and allowed voice actors/actresses to reprise their roles (e.g. Bloo and Omi) and host seasonal blocks filled with back-to-back episodes and phone-in competitions (until the latter got banned due to scandals).

10 years ago, they got extremely lucky and managed to rein in all three voice actors for Grim, Billy, and Mandy. Unlike the other two occasions mentioned in the last paragraph, where it was all done live, the Billy & Mandy blocks were all pre-recorded. In addition, until Uncle Grandpa popped his head in last year, the trio were the last new cartoon hosts of a seasonal block in the UK. [Omi would be the last, returned by popular demand]

[Note: the music would roughly be the same as that used for the new version of the "War of the Worlds" stage show, with apologies to Jeff Wayne] Next morning, a crowd gathered on the Common hypnotized by the unscrewing of the cylinder Two feet of shining screw projected when suddenly the lid fell off

A humanoid robed woman, heat radiating from her, appeared above the rim A huge short-bodied girl, larger than a skyscraper, rose up slowly a flower pattern festooned her pink shirt Of which the woman stood on top of as she and the giantess barked out her orders to two bicycles that changed into robotic lifeforms

A few young men crept closer to the pit Instantly the empress-like woman emitted an invisible ray of heat Which leaped from man to man and there was a bright glare as each was instantly turned to fire Every tree and bush became a mass of flames at the touch of her mighty fire manipulation powers