This is a very EASY April Fools joke...
Simply take a large potato chip and place it on the front seat of your loved one's vehicle.
Now for the overacting part (to make it seem like they have a chip in their paint)! Say something like this while shaking your head in disgust,
"Wow! Did you see that big chip in your car?!? It's huge...
I wonder how that happened? Where'd you go today?"
The kidlets did this for hubby a few years back...and they thought it was a hoot!