In the first case you can grab Phantasmal Image, Dockside Extortionist, Derevi, Empyrial Tactician, or Grim Hireling
Not only can you draw an absurd amount of cards off it, you can also give all non-humans +3/+3 until end of turn if youre looking to end the game
Him being flying certainly helps, as well, although it's really more the first part of the equation that brings people here most often
There are too many efficient options that can shutdown these decks, especially ones that don't have countermagic
Mickey Mouse - Brave Little Tailor has an ink cost of 8, meaning he's hard to summon
I assumed Ariel would be the chase card of Ursulas Return even before the set came out