Some are guaranteed in a particular product, whereas others are only obtainable through some special promotion
TCGPlayer puts Goofy - Super Goof's value at $318, so although he's not quite at the very top of the value ranking, he's still up there with the best
The tricky Rankle, Master of Pranks is another mainstay, a mythic rare from Throne of Eldraine floating around $12 or so
Morophon, the Boundless Morophon, the Boundless helps you to build the typal deck of your choice: it's the best shapeshifter in Magic so it can be any creature type you need
The main line of play is simple but powerful: develop ink early with Sapphire, then drop mid-to-late-game glimmers that generate Lore more efficiently
Looks like a weird gimmick