Always check your envelopes before re-using them - you never know what your recipient might find as an extra free gift!
I sent my sister Oli a parcel for her birthday. She lives down under so you have to send things well in advance and although it wasn't that long ago, I had totally forgotten what I'd sent her, and I haven't even had the baby yet! It also took her a while to ask me if what she'd found was meant to be in there...
But before you get excited it was nothing sinister, just one of my contact lenses.
She thought it was a sweet way of me keeping my eye on her... ;)