Back in the days of VCRs - hit the eject button - and out slide these colourful little felt finger puppet faces - the elephant looked particularly surpirized. To my 3 year old son that slot was the most sensible place to store them. And I got a free puppet show.
When I owned a 1989 Thunderbird Super Coupe, its CD player was not a tray but slot that automatically pulled in disks when fed. The owner’s manual said it’s “not recommended” to use the smaller than standard size CD’s, but I fed it one. And soon had to discover how to remove the drive from the dashboard and open it to take the disk out. Don’t try that either.
My son used to put loose change into the seat belt slot on my Jeep. One time I put the belt on and it locked forever since the void spaces were solid coinage and the spring steel could not move. It took over 15 minutes to work enough slack into the system that I could slide feet-first onto the ground. Had to replace the entire seat belt.