Biography
Greg attended Jack’s 21st birthday party, at which Chris (while invisible) got super drunk and could barely remember the event afterwards. This was the last time Jack saw Greg. (That friend you haven't seen since high school)
After the party, Greg disappeared (metaphorically) from Chris and Jack's lives, and was secretly recruited by a secret government agency.
He forgot to order compressed air to work the gyroscope for the shaky light room place, angering Agent 17. (Playtesting a top secret video game)
During a mission, he mistakenly killed both Pete and Pete’s clone. (Ask me something only I would know!)