Isabella was the imaginery friend of Clara Sutter, one of the children aboard the Enterprise-D. When a spaceborne entity came aboard the Enterprise in 2368 to investigate the ship as a potential energy source for its race, it appeared in the form of Isabella and befriended Clara. The entity departed the ship when it was made aware of its negative impact on Clara. (TNG: "Imaginary Friend")
- Some information taken from the Star Trek Chronology.