Design: Turnip has this cute duck-bill thing going on. It's a unique design and he looks spirited enough to actually be relevant (unlike Neo-Fio).
Combat: It's nothing radical, but he does get funny tech names and a double tech.
Tilt: Kato hinged the entire ending of Cross to suggest that there's a "Kid" or equivalent out there for all of us (and perhaps by extension, we should all dream and change our own history as Chrono Triggers). Of course, this completely backfired, as pretty much everyone interpreted it as canonical and those who guessed that it really was Tokyo weren't any closer to getting the theme.
But Turnip is the opposite: he's a thematic gesture done right. Taking him to the sleeping Dragoon sparks insightful dialogue and pondering. Turnip becomes something special as a dream being, and it's such an attractive concept (coupled with that design) that Ill give him an A. Masa, Mune, and Doreen were interesting too, but Toriyama made them butt-ugly alien ripoffs.
So, let this thread begin. I can't wait to hear all the Ds from the people who never saw this scene or just have it out for Chrono Cross.