Melissa Joan Hart was really cute and funny in this Nickelodeon production that ran for five seasons 1991-4. It's easy to see Sabrina the Teenage Witch in genesis. Very similar line delivery and those amazing fully-articulating eyebrows. She was born with two teeth missing (later fixed). The gaps on either side of her front teeth are real.

In "Brain Drain", Clarissa has smartness on her mind. Although brother Ferguson shows some classic signs of being smart, Clarissa is not absolutely sure and she's always looking to put him in the crapper.

In each episode Clarissa converses with the viewer (explaining the inner workings of life and the hardships of growing up). At the end of this post are a couple of compilation videos. The pics are moderate quality.