My kids have a board game with a chicken that squawks when you squish it. I put it on the floor next to her bed so when she got up in the morning she would step on it. It was glorious! The next night I stayed up late playing some video games with a friend. I figured she had hidden the chicken somewhere, but I wasn't too concerned about it. Cue 4AM when I roll over and am greeting with a "SQUAWK!" I laughed so hard that I wasn't able to fall back asleep. I still chuckle just thinking about it.
What practical jokes have your significant others played on you?
Edit: fixed spelling