These are 4 characters drawn in the Advanced series art style (as it's most commonly thought of, although it was also used in a lot of early 2000's JumpStart books). From top-left going clockwise, the characters are the Color Meister from JumpStart 3D Virtual World: Quest for the Color Meister, Sybil from JumpStart Reading for Second Graders, Sunny Skunk from the JumpStart Academy series, and Flap from JumpStart Adventures 4th Grade: Haunted Island. The character selection is a bit random, but none of these characters were ever canonically depicted in this art style, hence why I chose them. It was fun to reimagine their designs in this way.