Frog was a bit of an odd character in Chrono Trigger. He didn’t want to get involved at all at first, not to mention being cursed to look like a frog, and it takes several run ins with him to get him to join the party. I also thought it was kind of strange that you could break his curse by not recruiting Magus, so he ended up with an entire other sprite sheet for his character. Considering how old this game is that was probably a lot of effort for one small detail that not all players will even see.
In designing the kit for Frog I was using the same kind of rules as my other Chrono Trigger kits. I wanted an interesting pose that wasn’t him just standing around, so a battle pose, preferably with his sword in hand. I ended up choosing part of the animation he uses after finishing an attack, leaping backwards to get back into position.
You can find his kit on Etsy here: http://etsy.me/1UJcUNr