Every distinct wording since 2010, newest first.
April 22, 2021 · Strixhaven
Once you take the special action and put the card with companion into your hand, it remains in the game until the game ends.
April 17, 2020 · Ikoria
As a mutating creature spell resolves, if its target is legal, it doesn’t enter the battlefield. Rather, it merges with the target creature and becomes one object represented by more than one card or token (see rule 721, “Merging with Permanents”). The spell’s controller chooses whether the spell is put on top of the creature or on the bottom. The resulting permanent is a mutated permanent.