Repsac

Repsac, also referred to as Random Threat by the bugs in the spider web, is a menacing ghost who serves Ms. Grunkle in JumpStart Adventures 4th Grade: Haunted Island.

JumpStart Adventures 4th Grade: Haunted Island (1996)
Repsac occasionally springs upon the user to ask multiple choice questions that will deplete the user's health if answered incorrectly. Most of his questions seem to involve science & grammar, as well as sentence structure. This is presumably due to the fact that the game does not have activities which specifically address these topics.

Trivia

 * Repsac is "Casper" spelled backwards, which is quite fitting considering that Repsac's personality is the complete opposite of Casper's.