Playable characters

Playable characters from the Theory of Nicole series.

Original playable characters
These are the following playable characters in the original game and all the games after it.
 * The ten-foot atomic-powered plankton
 * Sophie the Otter
 * Catherine the Spellcaster

Other playable characters
Nicole Birou-Jennings is a playable character in Theory 2 and all the games after it.
 * Nicole Birou-Jennings (since Theory 2)
 * Vitalia Urbansza (since Theory 8)
 * Richard Drien (since Theory 8)
 * Malek the Magician (since Theory 10)
 * Reicheru (Rachael) the Yokai Spirit
 * Gemma the Good Witch

Former playable characters

 * Jo Frost (Theory of Nicole, status: ended)
 * Planktonine (Theory of Nicole-Theory Animated, status: Secret Agent)