What is the name of a show about chalk that was on Nickelodeon?

There wasn't a Nickelodeon show specifically about chalk. There are a couple of shows that you might be thinking of:

* "ChalkZone" - This show features a boy named Rudy who uses a magic piece of chalk to enter a magical world called ChalkZone.

* "Doug" - While not about chalk itself, Doug's drawings were a big part of the show and often served as a narrative device.

Do you have any other details about the show you're thinking of, like the time period or the characters?