This is the shortening of a catchphrase that was transformed into a meaningless term (as of now) to call someone in any situation. The catchphrase is often said by a character I created called Wago, the catchphrase being "Whilly wagger wag!"

A Whilly Wagger could be an annoying person, a intimidating ambusher who catches you by surprise, a nuthead, a dangerous immortal being, a person who is part of the Whilly Wagger gang, a psychotic killer ball, and a speedy delinquent. That's how I use it anyway.
Example:

Stupid kid: Nightmare is real!!!!
Me: I can't believe that you're so absurdly delusional that you think one of MY cartoon characters is real and is somehow walking despite having no legs!
Stupid kid 2, 3, 4, 5, etcetera: BUT NiGhTmArE iS rEaL aNd YoUr HiM aNd YoU wAnT tO kIlL uS!!!!
Me: You're a Whilly Wagger! You know that? You're a real Whilly waggin' fool!
by WhirlPool Waters November 30, 2022
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