Quote from Att »If I was to use Tentative Connection on an opponents creature, and then mutate it,
702.139a Mutate appears on some creature cards. It represents a static ability that functions while
the spell with mutate is on the stack. “Mutate [cost]” means “You may pay [cost] rather than
pay this spell’s mana cost. If you do, it becomes a mutating creature spell and targets a non-
Human creature with the same owner as this spell.” Casting a spell using its mutate ability
follows the rules for paying alternative costs (see 601.2b and 601.2f–h).
Quote from Att »whether I mutate it over or under my opponents creature. Does the game recognize the card anymore in either fashion? Does it change regarding position?
702.139c 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
721.2. To merge an object with a permanent, place that object on top of or under that permanent. That
permanent becomes a merged permanent represented by the card that represented that object in
addition to any other components that were representing it.
721.2c Because a merged permanent is the same object that it was before, it hasn’t just come under
a player’s control, any continuous effects that affected it continue to do so, and so on.