While I personally have never had the urge to try this, I know full well my nearly 6ft, 182lbs frame would never fit and getting out would be awkward. Imagine asking for help in that kind of a situation? What would you even say? Would they need to grease or butter you up to get you out?
Anyways, the reason I'm replying is because I went grocery shopping with a friend and his girlfriend a while ago and she decided to see if she could fit into the child seat of the buggy. She actually fit and when she couldn't get out, she pouted and motioned for my friend, she even said, "Daddy, I need out". Needless to say, that put a smile on my face and it had me thinking, if only they knew
So yeah, something I would never try, but I know people who have tried it.