I've seen folks bag empty rows during the climb out. I recall having my eye on a row with three empty seats in the middle and thinking I'd snaffle that as soon as the Belts went Ping.
Within a minute of rotation, a young man had slipped his belt, dived across to the row and got comfy.
By the time the Ping went - he was stretched across all three, wrapped in a blanket and the seat belt correctly fastened across the outside. The crew would have been hard pressed to to get him to go back to his original seat since his only crime was ignoring the belt sign.