No sacrificing, they have to fight.

But, if you want a real reason, how about this.

Chief got reports of missing children from Wonka's factory. Brian and Penny are on vacation on... Mars. So, Gadget tracks Wonka to some empty place that is nuetral for both of them, where he just turned a kid into a piece of candy, then ate him. Then he saw Gadget, and they fight.

Then Gadget would win because he is unstoppable against villains, especially ones that hurt kids.

How is Gadget unstoppable against villians that hurt kids? He's never shown any sign of being unstoppable against villians that hurt kids. And Wonka could
BS his way through Gadget. "No, that wasn't a kid, it was one of my experimental candies. Would you like a piece?"

I'm reminded of that one idiot kid who had a red cape and blue pajammas when I think of Gadget saving kids...

[Edit]And, IHMN, you just gave them a reason why they're fighting, thus cnradicting your earlier statement.[/Edit]

Wonka would never do that. He let the kids screw themselves, and Wonka went and fixed the little bastards up again once he was done (okay, that one kid was permanently blue, but that was about it.)

He would no more eat a kid than Gadget would slaughter a tribe of Oompah-Loompas.

...

Okay, here's a non-factory setup: Wonka is on vacation , having taken his Great Glass Elevator to the Carribean (Charlie's taking a hand running things back at the factory). He's incognito, so he's wearing bright yellow Bermuda shorts and a pair of giant sunglasses. Along with his purple top hat and waistcoat, because incognito is well and good, but you've always got to have style.

While also in the Carribean, Brain and Penny have been kidnapped. So Gadget, 'investigating' their kidnapping, does as Gadget does and decides the 'criminal' is some random guy who has nothing to do with anything in any way. In this case, he sees Wonka on the beach, and seeing his sunglasses decides that this must be the dastardly kidnapper. So while Brain and Penny are about the business of freeing themselves and foiling the kidnapper's plot, Gadget barrels down the beach hollering "Stop! Thief!"

He only did it to ease Dragonbane.

I say...hmm...Wonka, just because Gadget wouldn't realize he was supposed to be fighting, and would get tied up by Ever-Extending-Non-Chewable-Chewing-Gum that Wonka was testing. All Wonka would have to do is say that its a good stress reliever or some such BS and Gadget would go along with it.

[Edit} Fifthfiend, one problem, your situation involves Penny and Brain not just being on the same planet, but the same immediate 100 miles. They'd escape and help Gadget. We need to ship them off to Pluto to make it fair.

After kidnapping Brain and Penny, Dr. Claw's henchman takes them to Pluto.

wouldn't Wonka even try and explain that Gadget was incorrect? Now........if that DID happen, Wonka would win. I think he's some kind of spellcaster anyway...

Gadget still loses. Wonka just has to act confused, then offer him some extra-sticky-stucko-gum and Gadget gets frozen up.

Gadget wouldn't get frozen up. He would get sticky, then try to escape by extending his arm, which would take a while but eventually the arm would suddenly shot out because of the force he was using to try and move it, which would then smack Wonka right in the face and knock him out.

I doubt Wonka would be stupid enough to just stand in front of Gadget...