Conceptially it's a great idea, in terms of ease it'd be a bitch to draw.
Not to mention the formatting so that they push together properly.
I suppose it could be done if someone were to draw a whole car, as wide as an SC panel, then cut it down the middle and separate it into the two necessary halves.
Formatting is easy enough, you just make each pic exactly 125 pixels wide and push it to the edge of the canvas. You'd really only draw one half of the car and flip it when you add another character (so you can have 2 different people together).
The difficulty is drawing a character the same size as the characters already in use that fits into that space, while still having the car look like a car. And then doing it in a way that works with all the backgrounds, so the car doesn't look out of proportion. A lot of the backgrounds only have a finite amoutn of "space" where the car could be- eg; the bedroom- you can have both a cropped character or a standing character fit in between the "front" of the panel and the bed, but trying to make a car fit into that area is a lot trickier. Really the car would have to be wide enough to fill the whole panel, and crop the sides off at the edge of the windshield- this would hide any background inconsistencies behind the car, but prevent it being used one half at a time.
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Dinosaurs had eggs bro, the chicken came way later.