Season 3 Episode 16 - Urgo

SG-1 travels to a paradisical-appearing planet...only to step immediately back out of the Stargate with no memory of their trip. They soon find themselves engaging in odd behavior, and find out that a computer chip has been planted in their minds during their memory blackout. The program in the chip, Urgo, can manifest as a friendly looking, curious entity that only they can see because it interacts directly with their perceptions. Urgo can influence their actions, and doesn't want to be shut down or sent back to his creator. The team have to contact Urgo's creator, Togar, and convince him to remove the chips or shut down Urgo.