My dad did this when I was a kid.

I used to just let anything fall down the space between wall and bed - clothes, toys, etc. - and one day I saw a big spider chilling on the ceiling above my bed.

Naturally, as any little girl would, I fled the room and begged my dad to get rid of it. A few minutes later he returned and told me he had killed it, but the dead spider fell into the abyss behind my bed and he had not been able to recover it. I cleaned that mess up right away but never found the body...

When I told my mother about the mystery of the missing spider corpse, she looked at me for a few seconds, shook her head and said "Oh no, he did not." I only got it a few years after that. :)