Sir-Haunts-a-Lot

Sir-Haunts-a-Lot was the disguise of an unnamed culprit, who wanted to steal Queen Guinevere's necklace from a museum.

Physical appearance
He was completely covered in a knight's armour.

Scooby-Doo! Team-Up
When the gang put all the clues together and pointed out the culprit behind, he instantly appeared in the armour, holding his sword. But he was knocked down and unmasked, by who was believed to be Shaggy Rogers, but turned out to be the Martian Manhunter in disguise.

Appearances

 * Scooby-Doo! Team-Up
 * #24.

Notes/trivia

 * How the culprit could suddenly change into his costume in a puff of smoke is unexplained.