tengo hambre

Because we see multiple times throughout the series that Evil Leafy is willing to immediately possess anyone as long as she can catch them, but she comes across Fries in the caves and is so utterly baffled by him not being scared of her at all that she waits a good majority of the challenge to actually do anything to him. He stands in one spot for a prolonged period of time, in the perfect position for her to possess him, and she chooses to instead keep appearing on either side of him to annoy him.

She is presumably doing this because she wants to find a way to make him dislike her presence like everyone else does, but by the time we see them again, Evil Leafy has neither possessed nor kept annoying him, and they have apparently become Best Friends, (according to Fries). Which you could argue isn’t actually true, since Evil Leafy possesses Fries right after he says it, but in my personal opinion, she did that purely to mess with Coiny, since after she’s kicked out of Fries’ body, she makes no attempt to repossess him in the fifteen-ish seconds they’re alone together again (even after Fries insults her!).

This is reinforced in the next episode, where we learn that apparently Evil Leafy liked or was interested enough in Fries to give him her number.

And Fries interprets Evil Leafy hanging up silently to mean he got ignored, but the next time we see Evil Leafy, she is taking what is presumably the fastest route out of the caves and to the challenge location, where Fries is. And once she catches up to Fries, she contradicts her past behavior by not only possessing Fries immediately, but also not attempting to go after anyone else until it is confirmed she cannot help Fries win the challenge. Which you could interpret as her hating Fries enough to only want to possess him, and only stopping her possession of him because she hears Needle invoke her name in vain…but I like to think she actually does like him now and wanted to help him win.

However, I also have a potential funnier interpretation, which is that since Fries asked her if she wanted to get something to eat, and Evil Leafy “eats” by possessing people and putting them in her pocket dimension, she thought he was asking if she wanted to come possess him, and she liked the way he tasted last time, so she came as quickly as she could and possessed him.

And then there’s obviously him celebrating her returning in BFDIA 25 while everyone else is horrified, which is hilarious.

I assume the writers wanted to make sure Evil Leafy had some sort of unique dynamic with another character for IDFB, and figured making Fries of all people friends with her would be funny. And it definitely is, they are one of my favorite duos. I like to think Evil Leafy has a personality outside of “be evil and possess people,” and Fries is the person it comes out the most with.