Origin

Can't Let You Do That (Star Fox) is a meme that's based off a line in StarFox 64 (also spawner of the infamous Barrel Roll), this line happened in the level "Fortuna" when the character Wolf O'Donnell leader of the Star Wolf team told Fox McCloud he could disarm the bomb at the base.

Line at 1:59

Formula

The consists of the character Wolf O'Donnell being shopped into situations either entirely or partially and all caps announcing: CAN'T LET YOU DO THAT [insert person/thing here] Usually the targets are things that rhyme with "StarFox" and occasionally actions sound like "Do".

Spread

The meme started on the 1st of April, 2008 on the Facepunch forums when user Aska49 said the following.

I need more sayings, in this format.

I can't let you ___ that, Star___!

So far I have.

I can't let you do that, Starfox!
I can't let you mail that, Starfax!
I can't let you brew that, Starbucks!

Anyone think of any more like that and I'll add them. Also, if anyone thinks of more triggers I'll add those too.

The other users came up with

1. I can't let you down, StarAstley
2. I can't let you dial that, Stargate.
3. I can't let you time that, StarClocks

Among others. See thread here

This picture was posted on Halolz on April 28th, 2008 where it picked up steam

Now this is popular among gaming forums such as IGN.