They were called Crashmobiles because that's exactly what they did. There were several models in different sizes, but the design was more or less the same across the CM spectrum. You would squeeze the sides and roof of the car together over a springy-lever connected to the front bumper of the car. Roll the car forward, bonk the bumper, and KAPOW. The lever would be triggered and the thing would burst apart, usually while the child operator was making horrific screaming noises ("aghh, gahh, my legs are broken, I've been decapitated, aghhh, agghh!!!). Then you would carefully gather the parts, rebuild it and repeat. Until the car broke for real (something that usually happened really fast) and you had to steal 20 cents from your Dad's sock drawer (sorry Dad) and run to the supermarket for another.
But you have to admit. There's something genius about selling a toy that's MEANT to be broken.
What the image below doesn't really sell is just how tiny the Crashmobile Jr. really was. Like, three inches long and maybe an inch across. Also, this image is from later in the life of CM Jr., which was a mere 19 cents when first unveiling. And finally, someone must have stored this one in their dirt closet, because fresh Crashmobiles weren't usually this dusty.
Anyway, crashmobiles. What can I tell you. As a child I was easily amused...