[Vivi]

I'm just going to start off by saying that every time I read the title of this thread I think you're talking about something else. But back on topic, she's sorely underused. I think the best episodes involve her more because of her connection to the kraang, who are at this point far more interesting than Shredder. And her best moments are usually when she's not around Donatello (eg. with Karai, with Splinter, finding that crystal ball etc etc...).