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Grookey: All of Grookey's foreign names reference music and rhythm. In it's first appearance it banged a rock with it's stick, perhaps creating a beat? Now if you follow the S/M/F theory Grookey could turn into a very feminine monkey. Perhaps a dark type to go with Greninja and Incineroar. Or maybe a huge burly DK-like Gorilla with huge wood bongos. Maybe a drummer Chimp? I could also see fighting, rock, fairy, or ground as typings.
Scorbunny: Scorbunny is obviously the speedy one of the group, and seems to have a soccer theme. Hence the bandages. I see a stealthy, speedy soccer playing rabbit. Or maybe they could reference the moon rabbit of Japanese culture and have it be very serene and graceful. Either way it's gonna be fast and lithe. Possible typings I see are electric, fairy, steel, or ground. No, it will not be a fighting type.
Sobble: Sobble is the one i'm most sure of. I expect a huge, ripped sea creature with bulging muscles, savage jaws and intense swimming prowess. I could also see a Loch Ness Monster theme, maybe a ghostly lizard, a theater theme has been suggested, or perhaps they'll be straightforward and simply have it be a dragon. I see fighting, ghost, dragon, or poison.