You pretty much need to load up any level/minigame and underachieve as much as possible to get a bronze medal, which is pretty much doing just the bare minimum of the level challenges.
Its unclear as to whether not you can get a platnium medal and unlock all the medal related achievements at once, as this game is buggy at best :/
YouTuber "BloodyGoodReviews," playing the level Omnidroid Bash from The Incredibles, gets a platnium medal here (provided as a reference):