When I was a kid we had a battery powered Santa toy just like the one in video related. It sat on a cabinet in the attic, forgotten and disused.
One day (I must have been 5 or 6 years old, at most) I was looking for some unrelated thing, and it had gotten into my head that said thing must have been taken to the attic.
As I went through a desk's drawers, the Santa toy caught my attention. It kind of frightened me, sitting there as if it was looking at me. So I bravely marched to it, flipped it over, opened the battery compartment and bam, no batteries. Slightly relieved it couldn't magically come to life and chase me, I went back to browsing through drawers.
After not even five minutes (which felt like an eternity, because I was still afraid) the fucking thing, still there in the corner of my eye, starts humming the tune and shaking its damn bell. I immediately darted down the stairs yelling for my mom, as the thing kept blasting the tune.
I don't remember clearly what happened after that. I think it quickly stopped, so I sent mom upstairs to check on it. There were still no batteries in it.
Caveat: there were old singing Christmas cards in the drawers I was checking. Some of them had some battery power left, and did sound off when I opened them, but none had enough power to be heard two floors downstairs. To this day my mom swears she also heard Santa's tune.
The end.