Can a sorcerer make independent spell-effect choices for a Twinned spell?

Question

Can a sorcerer make independent spell-effect choices for a Twinned spell?

For instance, the Polymorph spell can be used on willing and unwilling targets; the unwilling can make a Wisdom save to avoid the effects.

The sorcerer's Twinned Spell metamagic option creates a second instance of the same spell on 2 viable targets within range.

Does Twinned Spell force me to polymorph both targets into the same thing, or do I get to choose what each instance of polymorph does independently?

In this case I am trying to turn my friend into a T-rex, and an enemy into a goldfish.

Answer 1

You seem to have misunderstood Twinned Spell slightly. It doesn't cause a second instance of the spell to target another viable creature within range; it causes the same instance of the spell to target two viable creatures within range instead of just one. The relevant section of Twinned Spell reads as follows (emphasis mine):

... you can spend a number of sorcery points equal to the spell's level to target a second creature in range with the same spell.

This has a couple of implications.

First off, for spells like Polymorph, both of the creatures you're targeting turn into the same creature. However, you can keep concentration on both creatures, as it is only one instance of the spell, as opposed to two.

Secondly, for spells with a damage roll (like Chromatic Orb), you roll the attack roll separately for each creature, but you only roll damage once.

For spells that require concentration, both creatures are affected by the concentration effect. For example, if you cast Twinned Witch Bolt, if you hit both targets, you deal 1d12 lightning damage to them on the first turn, and you can use your action to deal 1d12 additional damage on each of your turns to each of the targets. If you fail a concentration check, you lose concentration on the spell for both creatures, not just one of them. Whether moving outside the range of Witch Bolt ends the spell for one or both creatures is up for interpretation by your DM (a strict reading of the RAW would suggest it ends for both of them, but I would personally rule that it only ends for the creature moving out of range).

In short, your polymorph spell turns the two targets into the same kind of creature.

Answer 2

Yes, you can - Twinned Spell doesn't prevent you from making different choices for each target.

The sorcerer's Twinned Spell metamagic option says:

When you cast a spell that targets only one creature and doesn’t have a range of self, you can spend a number of sorcery points equal to the spell’s level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip).

As written, this could be interpreted in a few different ways. the ambiguity is also acknowledged by Lino Frank Ciaralli in a comment on xanderh's answer:

Nothing in twinned spell metamagic says anything about [...] not being able to choose from among multiple [e]ffects from the same spell.

Without any explicit rule preventing it, it seems reasonable to assume that different choices could be made for each target; the actual casting of the spell only occurs once, but you're ostensibly producing a separate effect for each of the two targets.

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Rules designer Jeremy Crawford unofficially concurred with this ruling in a tweet in October 2017:

Twinned Spell. Chromatic Orb: can you pick another damage type for 2nd target? Polymorph: can you pick a different beast ?

Twinned Spell doesn't require you to make the same choices for each of the spell's targets.

In the absence of any rule forcing you to make the same choices as part of that same spell, you can indeed make different choices for each of the two targets of a Twinned Spell.

In your particular example, you could indeed target an ally and an enemy with polymorph and use Twinned Spell on it, turning your friend into a tyrannosaurus rex while turning the enemy into a goldfish (...well, there's no statblock for goldfish, so let's say it's a sea horse).