I mean, it's a fresh face among the group. (Though Mr. L is too, just arguing with Bowser)
Mirage just hauled back a big supply of bananas for the crew, so that's something Frog could react to if you want to take that route. I'm also looking for an opportunity for Mirage to actually learn about Spirits and how those work, so maybe we could make a situation for that in the near-ish future. That's just me assuming Frog knows how they work, though.