A Date with Rosie Palms: Red mentions how Blue likes to "play with his joystick". Earlier, we see Red listening in on what sounds like Blue masturbating, but is actually him knitting a hand towel of Olivia Munn. Then he decides to jack off, but we don't get to see it.
Dark and Troubled Past: Raccoon. His own father betrays Japan and becomes a demonic warmonger, forcing Raccoon to slay him, his family is eaten alive by his father's pet demon octopus, and in the end, he's blamed entirely for the death and destruction his father caused and is forced to leave Japan in disgrace.
Mood Whiplash: To serious extents after Red and Blue escape the Takagami ninjas temporarily. While they sail away on a boat, after a while Blue realizes that Red had only saved him from the bullies on his first day of school to impress the ladies, and wasn't actually his friend. Blue doesn't take it very lightly.
More Dakka: Lord Tourettes deploys a minigun from a helicopter and uses it to gun down a lot of enemies.
The Reveal: Red actually saved Blue from the bullies back in their youth to impress the ladies, not for Blue. And the only reason he's stuck with him throughout the series is because Blue's the only one naive enough to keep putting up with Red's behavior. That means they were never actually "friends" to begin with. Blue is understandably pissed.