If Mishra's Foundry becomes a creature and you haven't controlled it continuously since the beginning of your most recent turn, you won't be able to activate its first or last abilities, and it won't be able to attack (unless it somehow gains haste)
Look at the original printing for fling: Back then Planeswalkers didn't exist as a card type, spells that were meant to be able to target anything (that could take damage) had the wording "target creature or player"
This dropped everything below it, and Crop Rotation fell off, making it number 14, but I left this paragraph here, already written, so you could see what card was next)
Phase two Perform any of the following, in any order: Place a Basic Pokmon card from your hand on your Bench face-up
Silvar, Devourer of the Free eats humans to grow
Lets say that you have [c]Blightsteel Colossus[/c] and your opponent attacks you with their [c]Worldspine Wurm[/c]