When my ds (now a worldly 5) was much smaller he had a beloved Little People dog - called imaginatively Dog.
It was small (er, yes hence the name Little People) and I was forever looking for dog. So I did as so many others here have done and bought an extra (for emergencies) and stored it in the glove pocket of the car.
One dark and stormy night, driving the dc to my Mum's on a revolting M6 the cry went up "Where's Dog? I've lost dog!". There was much wailing.
I felt relieved, nay, smug even, as I reached across, took out 'dog mk2' and passed him into the back.
A small voice wailed 'This isn't Dog! This is funny dog!'. I tell you I could have sobbed!
When we eventually reached my mums house some 2 rather fraught hours later I looked at Funny Dog. His eye patch had been printed in a slightly different place.
How my son could tell this, by feel, in the fucking dark, I still do not know.