Answer:
To connect Sergei's uninterested and tedious personality.
Explanation:
In the story "What, of this Goldfish, Would You Wish?", the author includes the goldfish, an example of a magical being archetype to connect Sergei's uninterested and tedious personality with the events of the story.
Though Sergei had found a magic goldfish that could grant him three wishes, he wasn't excited about it. He used two out of the three wishes on his sister and Sveta's son until he had to use the third wish to undo what had been done to Yonatan.
The whole story revolves around Sergei's decision on how to use his third wish.
