Populate instructs you to create a token that is a copy of a creature token you control (CR 701.25). The rules place no restriction on the origin of that token — only that it currently exists as a creature token on the battlefield under your control.
A token that was created as a copy of a non-token creature (for example, via Cackling Counterpart or Fated Infatuation) is still a creature token. It simply has the copiable values of the original creature card it was made to resemble. That token is a perfectly legal target for Populate (CR 701.25a).
When you Populate that copy-token, the new token is a copy of the existing token — meaning it inherits all the same copiable values (name, power/toughness, abilities, etc.) that the copy-token has, which trace back to the original non-token creature (CR 706.2, 706.3).
Example: You use Cackling Counterpart to make a token copy of your opponent's Grave Titan. You now have a creature token that is a copy of Grave Titan. When you cast Trostani, Selesnya's Voice and use her Populate trigger, you can target that Grave Titan token and create another token that is also a copy of Grave Titan.
The key point is that Populate cares only about the token's current existence as a creature token, not how it was originally created (CR 701.25a). Tokens that copy non-token creatures qualify without restriction.
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.