That was Fun is an e-mail you received after completing the mission Investigate Jizan Weapon Stockpile if you didn't sound any alarm in the mission and you killed any enemy in the mission.
Message[]
From: Sean Darcy
To: Mike Thorton
Gotta hand it to you Mikey, that was some great work out there. No alarms, no nonsense - just dead terrorists bodies to bury. That's the way every mission should be - in like a shadow, out like a horseman of the apocalypse.
For the record - I'm not saying I couldn't have done better if they sent me. Next time, I'll be in the field and you can sit back and play handler.
Peace,
SeanD