Say hypothetically, one were to custom make their own mario funko pop, and sell it on ebay or etsy would that be illegal?
You can mbake, market and sell your own toys but not legally use another manufacturers name or methods. Some people make, build and sell their own Lego character "minifigs." This is fine so long as they indicate the item has been "customised" so they cannot be accused of inappropriateness. Some "original" minifigs are quite "rare" and can attract a substantial sum for their unique qualities. It would be "fraudulent" if someone customised a minifig and offered it for sale while claiming it was an original.
Yes. Thats copyright infringement.
yes but it would probably take more than one mario pop before nintendo notices. when it comes to making things based on licensed franchises, you really only allowed to do it for yourself or as a gift. 2d art might fall in a grey area though as i know a lot of artists sell art based on anime, games, and cartoons for conventions or as a source of income year round.
As long as you dont call it a funko pop, i think you should be good