I get headrushes pretty frequently too, depending on how long I've been sitting, but most commonly in the morning. You've got some sort of freakish delay though.
Hmm, I've never thought about the term before now.
Nahh, I get dots .____.* At my worst, they're primary colors; first is blue, then red, then yellow. Otherwise, it's usually a purple-gray mix.
Lol, I suppose it is... odd O_o;

@Desbreko:

I usually stop walking unless I've memorised the layout of the room for the next few steps in about a five-pace arc on either side because if I keep walking I may veer off and run into a wall. So open areas are usually okay, but close interior spaces tend to be a bit more interesting.

Especially if stairs are involved.

@AnimeArchAngel:

No, it happens if you go from a more horizontal position to standing full upright very quickly because all the blood is draining from your head.

It just happens more frequently to us tall people because our blood takes longer to get back up to the top.

Oh good, so I'm not the only person that happens to. Phew. It always happened to me when we were in gym and had to stand up for the Pledge of Allegiance. It's more foggy than anything.

Is it only supposed to happen if you're tall, though? I'm pretty small.

Never had that happen to me, not that I can recall anyways. Maybe it was due to me being in Wrestling. You were constantly standing up or being tossed down. So....*shrug*

My vision goes completely black when this happens to me really bad. If I've managed to stand fully upright before it hits, though, I can usually keep my balance as I walk.

That happens to me too. I'll get up out of bed, and half way into the kitchen when I'll notice, and then have to lean against the counter because it's so bad. x_x;

The world spins for me. Everything feels further away.

So I'm not the only one who sees in pixels during a moment of bodily instability! That's a relief.

Other people get fogs. I get pixels.

I know exactly what you mean. I definitely get that too. Except, rather than being produced by a headrush, my vision goes all pixelated when I'm on the verge of passing out. Which has happened maybe more than it should have. o3o

I get those when I stand up sometimes, too. Though I'm usually only able to get a few steps before I need to hug a wall, though. The rainbow waves are interesting.