This is a great way to keep one of your strongest creatures on the board against your opponent or an even better way to steal one of theirs
If the chosen permanent is copying something else (for example, if the chosen permanent is a Clone), then your Malleable Impostor enters the battlefield as whatever the chosen permanent copied, with the stated exceptions
Sometimes its worth a small fraction of a mana and doesnt increase cost, as on Anchor to the Aether or Veteran Motorist
You could tell me Oko was banned in Wizards Tower and Rainbow Stairwell and Id believe you (I didnt make those formats up)
Jumpstart -designed rares, uncommons, and commons can be found in non-foil and traditional foil in Set Boosters, with only non-foil extended-art rares found in Collector Boosters
This card builds a board state, fills the curve out, pumps creatures, and then helps with card draw, all for very reasonable prices