Daphne's glass of water at the Burger Binge disappears when she agrees to go to WrestleMania.
Cookie's leg brace is over his clothing when it would realistically be underneath (especially when there are more comfortable fitting ones out there in real-life), but having it always visible is better for the audience to know it's there.
The stadium's commemorative display has a WWE City News front-page report from the 1910s, on how Sin Cara Grande saved the day from the rogue bear. Yet the story establishes that WWE City was built (on the same site) only in the 2000s.
Are the gang that incompetent that they would leave Shaggy (and even Scooby) to pack their bags for the trip? (Fred even seems amused by it.) Even if they did only wear one outfit they would still need another set of fresh clothing, not to mention underwear. They also apparently went without a toothbrush and slept in the exact same clothing the entire time there.
Shaggy doesn't know what "accomplice" and "schematic" mean, even though these words should come up frequently in Mystery Inc's investigations.