We've gone with 'Ten Guy' for the name of this meme, even though you might have come across him as 'Really High Guy,' or 'Stoner Stanley.' His happy but slightly vacant expression gives us the impression of somebody who's having a good time, but doesn't really know why.
As the caption to the meme on the left suggests, he's often been used as a visual aid to remind us of all the silly little things we do when we're not thinking about it - for example, turning down the radio in the car in order to help us to read. There's nothing wrong with his face though, and he hasn't been captured in a moment of intoxication; he just happens to look like this, and judging by the photo on the right-hand side, he's this happy all of the time.