If you are walking while lying on a bed, you slide a bit out of it.

Like I said in the discription, if you are walking and rightclicking on a bed while it's night or a thunderstorm, you will lay down, but slide a bit out of the bed.

Steps to reproduce
1. Place a bed, it works the best, if the bed has no blocks right next to it
2. set the time to night
3. walk towards the bed (you can also walk backwards or sidewards -
    also its possible to stand on the bed and walking away from it)
4. while walking, enter the bed
5. watch how you slide in the same direction you moved towards