Något hände under säsong 1-finalen som inte kommer fram till slutet av säsong 2. De första ledtrådarna var i 2x04, Crackers Do not Matter .
Medan jag aldrig riktigt märkte det som elakhet (mer som irritabilitet), gör han lugn ut lite senare.
För fullständighet i det här svaret är detta vad du lär dig i slutet av säsong 2:
In short, Crichton is slowly going insane due to the neural chip placed in his head by Scorpius.
Harvey's appearance in Crackers Don't Matter was originally supposed to be nothing more than a hallucination, but the writers decided Scorpius needed a more-constant presence to be a big enough threat to the main characters, so the existence of the neural chip was retconned in to the events of the Season 1 finale by way of flashbacks.
In the season 2 finale, the neural chip is removed, but Harvey remains. At this point, Crichton gets more control over Harvey's appearances, since the personality doesn't have a physical presence backing it anymore, and isn't quite as wound up.