This nickname was actually suggested by my friend, but it was so perfect I just had to use it! That name was Buttmunch... it's both condescending and cute at the same time, I love it!
As for female characters, it has to be Leaf for me. She is a wonderfully written in this novel! It helps that I don't know much about her in the comics and other media, but that only made experiencing Leaf's character all the more enjoyable! She has an ego, makes snarky comments, but not in a spiteful way like Blue. Rather, Leaf has that playful vibe to her, even she can be self aware and have remorse sometimes.
She's just really interesting, and I look forward to seeing the direction her character goes in for future demos.
I also really liked Hilda and Flannery, whom are definitely top of my romance list.
Pikachu's nickname for me is Jolt, nothing interesting really, but I suppose I could've been referencing the Transformer character Jolt: who apparently is a mischief maker, so maybe that's where it came from.
It might've even been my brother's nickname for Pikachu in a game once.