I'm writing here to prove I didn't make this up.
In the 1970's when McDonald's had a menagerie of Krofft-like mascots including Grimace, Mayor McCheese, the Hamburgular and Ronald McDonald, Burger King offered it's own cast of characters including the Burger King and his royal foil: the Duke of Doubt.
Screenwriters say your movie is only as good as your villain, and the ongoing Burger King "story" features a disturbing putty-nosed bad-guy. The Duke bears a striking resemblance to the Child-catcher from CHITTY CHITTY BANG BANG. (A connection that would make sense to children of the 70's who grew up with such movies. Again, when I made this comparison my co-workers had no clue what I was babbling about.)
Hamburgular was Ronald McDonald's number one foe because he stole other people's food. Even in his criminal activity, Hamburgular is reinforcing the message that McDonald's burgers are delicious; so much so that he will break the law to obtain them!
But the Duke doesn't covet food-stuffs. His principle role is to question the King. He's like a villain in a Jacobean drama, lurking in the shadows and plotting against His Royal Highness. (The Duke also reminds me of Grima Wormtongue from Lord of the Rings.)
What I find most surprising in this ad campaign is that skepticism is portrayed as a bad thing. Kids are inherently curious, even suspicious. Doubt is a healthy part of any free society, it shouldn't be portrayed as villainous.
Well I hope you've enjoyed this latest installment of me taking the wrong things seriously. Maybe I'll do an entire series about advertising mascot's straw-men nemeses.