An idea me and Rainvaz got, basically you take the character you want then you make him star in an ad similar to the one you see in Mario Kart.
Here some ideas:
Antasma's Nightmare Fuel, Fawful's motors, Midbus Power Juice. Fawful Goggles. Shroob Lawnmowers. Mallow cotton candy. Geno lethal handcannons. Vim fuel 100% natural (need some black humor), Pi'illo island seats, Association for witches racing (with Cackleta, Ashley and Rosalina). A little hungry ? Feeling Tired ? Try Antasmunchies .
Want to solve crimes? Enroll in Pennington's detective school. Learn all the basics from the Penguin With an Improbably Large Brain.
Looking for romance, money, and thrills? Join Flavio on a glorious expedition. You do all the work, and in return Flavio will tell you many stories of raw bravery. No! It is no trouble at all!
King K's Minor League Tours. Learn all the basics of being a low-paid, minor league scrub by the master himself.
Waluigi Face Cream! Now you can look at beautiful as Waluigi!
The person who sells that will go out of business. Mario Mustache gel! Curve your stache like Mario do'! Wario Weights! Lift these to gain muscle like Wario do'! The Toad advertiser! Use this to get your shop used as much as a toad shop is!