Well, in 'Finn', the characters are made memorable through their relationships with each other. Finn's interactions with his friends or foes create interesting dynamics. For example, if he has a best friend who is always getting him into trouble but also helping him out of it, that kind of relationship makes both characters stand out. Also, the character development throughout the story is key. A character who starts off as shy and then becomes bold over time is very memorable.
The Unti Finn novel by A. J. Finn is a complex mystery that weaves together multiple plotlines and keeps the reader guessing until the very end. It's full of unexpected twists and turns.
The Fire Kingdom's Flame Princess could be an ally too. Her mastery over fire could complement Finn's powers in combat situations. Also, the various magical creatures in Ooo, like the gnomes or the fairies, could band together and support Finn. They might have their own ancient knowledge or magic that could be useful to Finn in his adventures with his godlike powers. Finn's kindness towards them in the past might make them more inclined to help him out.
He might meet some of the more reclusive characters in Ooo that we don't usually see in the show. Maybe a hermit - like wizard who gives him some cryptic advice.
Yes, Huckleberry Finn is often considered a picaresque novel. It follows the adventures of the protagonist, Huck, as he travels and encounters various characters and situations.