Here's a nice but simple piece of work from the days before Photoshop. Northern Towels wanted the boy on the wrapper to appear as though he were wiping up a spill with an actual towel on the table.
forced perspective. Forced perspective takes advantage of our brains' natural desire to make sense of the world in three dimensions, even when we're only seeing two.
The boy on the roll of towels is warped around the cylindrical shape of the roll. The extended arm is a paper cutout "peeling" off the roll hanging out in space there. The boy's arm is a vertical plane, perpendicular to the surface of the table. The way the arm is drawn just makes it look dimensional, allowing your brain to happily assume the boy is a drawing come hideously to life to wipe up your messes.
Also, paper children need the calcium and aliphatic resin that can only be found in glue milk, or "glumk" as they call it.