Hello! Actually I didn't find Twirly myself, I saw someone on the Pakka Pets Players Facebook group posted screenshots and decided to use them to fill the wiki! The description screenshots said something like 'no data found' (a bug on the pakka book that Whirly also had before an update). I still haven't discovered it myself, but the poster said they got Twirly after feeding it star treats, so I'll try to confirm this later. Whirly's description says there's another magic Pakka pet that evolves from eating candy so it's probably true! Sorry I couldn't be of more help!
(I forgot to log in to anwer this message the other day but it was me) I finally found Twirly myself! I can confirm it can only be achieved from feeding a pet mostly Star Treats. Also it seems Whirly is achieved from feeding it Blue Rock Candy specifically and not just any candy.