It happens when he's not looking and always seems to stop as soon as it starts, but it always happens. Every day without fail. He keeps a monitor for it because this planet's rotation changes, and it changes all the time.
Too fast.
Everything here moves too fast to chase down and his legs aren't long enough to catch it. (It's not his fault his legs aren't that long. He can't help it.) It's awful here. Too fast, too much, too loud, too putrid, too big, too cold, too hot, too smelly, too different, too different, too different and it never. stops.
It's awful here.
But it's not awful all of the time. That's why he monitors and keeps check, so he won't miss it. Today, there aren't any clouds to cover it up, and he gets a clear view.
It always happens, even behind the clouds. Even if he can't see it. Even if he slept through it. When the sun sinks below the concrete teeth of the city skyline, after the yellows leech into the orange and the orange drips into the reds, in that little fraction of time between the reds and pinks and purples, that's when it happens.
That's when, for a moment, the sky is the same color as Irk's.
It's not a perfect match, of course. Irk doesn't have clouds. The skyscrapers are taller, and the color's not this bright.
But it'll do.
It has to.
Zim thinks about the chemical composition of Earth's filthy atmosphere and the space between its Too-Fast sun and why it makes the same colors when Irk doesn't have any of those chemicals at all.
He does not think about how Irk's sky never seems to change.
He does not think about Irk's twin suns. (twin stars orbiting everything and everyone that matters, all-encompassing, untouchable, dazzling and beautiful and glorious, blazing hot and they don't think or care about anyone or anything at all and won't talk to him because the stars are stars and Zim is only Zim)
He does not think about how Irk's suns move so slowly and in tandem so that the color of the sky never changes. The color of blood and armadas. Always.
When Zim still went to Skool, before Dib stopped going to Skool and everything kept moving to fast and changed, he learned that Earth days are twenty-four hours instead of thirty-six. He learned that those years are only three hundred and sixty-five days instead of a clean four hundred, And because they only have one sun, they only have years and no cycles.
Cycles are long. Years are not. Years are a quick run through basic training or a trip between planets. Years are nothing.
That is how time works. That is how the universe works.
That won't work right here.
Earth's inferior sun is defective broken and that's why it goes too fast. (Not the sun's fault.)
Four years is barely half a cycle. It's like four minutes. Zim went to check his experiments for just a few minutes and when he came back, Bitters' class switched to a totally different batch of students. He blinked and the sun kept moving and everything changed.
Dib changed. He doesn't go to Skool anymore. Sometime between Zim closing his eyes and Zim opening them again, Dib grew.
He doesn't think about how tall. Tall enough to look down on him.
Dib doesn't go to Skool anymore, but Zim does.
Last week (month? decade?) they put a "playground" here on the hill, so all the disgusting human grubs could squelch around in the mud and squeal like the filthies they are,
By coincidence–just a coincidence–it's the only decent place to see the sky when the sky turns good for that short little moment.
Irk makes sense.
Earth does not.
When you receive a new assignment, you do not return to the old one. Dib does not go to Skool, so he should not be at Skool. He doesn't play, so he should not be at a playground.
And yet, even so.
He found him staring at the sky from the playground, sitting on the swings, rocking gently in the air while his too-long, too-big legs dragged his too-big feet through the grass.
He glanced over when Zim quietly joined him. Didn't say anything. Smiled a little bit.
They watched the Earth sky shift into Irk sky.
Watched the Irk sky shift into darkness.
With his shadow stretching and wriggling over the grass, the Dib tucks up his legs and swings on a seat too small for him. Zim glowers at such pathetic swinging skills. He demonstrates the superior swinging skills of Irk's finest.
Just before the sky goes dark, the stars come out.
One, two, twelve.
Dozens.
Hundreds.
The stars are the same wherever he is. Everywhere, the stars go on forever. Even here.
It's awful here. (But not all the time.)