Forget everything you've read about video game development, what you really need is more silliness. At least this is true if you're the creative driving force behind games for what is fast one of the most successful pieces of hardware in gaming history (phew...).
For example, let's say you are Nintendo's Shigeru Miyamoto. Let's say you're explaining your design philosophy to a magazine such as
Rolling Stone. Here's the development secret you would spill:
"The typical pattern when we're developing our games is that the development teams will work very diligently to make the game and I'll take a look at it and say "why does this game feel so serious? You need some more silly things in there."
Simple as that... although it does make it sound as if Shiggy is the David Brent of game design. Anyway, we now expect
Call of Duty: World at War to include clowns as DLC.
GTA IV's own DLC should include whoopy cushions. And as for
Resistance: Retribution for PSP.... how about banana skins?