What childhood prank did you play that seemed pretty tame and harmless but on reflection, could have had serious consequences for the pranked person?

Oh so many things! They were done in complete innocence of the damage that was probably likely if not did happen, it's lucky none of us as kids were hurt in the effects if there were any! 1. Throwing made up from mud and water, mud pies through a tiny gap which looked over the underpass of the train station when people were getting off the train. We thought it was hilarious, no one ever caught up with us because once they'd left the underpass we were back to our usual spot making friendship bands with embroidery thread. We didn't mean to look uninvolved or innocent, we were only interested in throwing the mud not waiting for it or the results. Don't ask me why this was fascinating to us, I still don't know now! I know if someone had words with us we'd have stopped and felt awful, but no one ever did. 2. We made a pond for frogs and then stole the frogs from the school playground to put in our pond. They seemed to stay for a while before moving away, there were some pretty nasty kids nearby and they'd regularly come by when we were all at home and they'd wreck the pond for no other reason than to upset us, so we'd build another pond, steal more frogs.... No one ever stopped us, we just wanted a pond with frogs, we didn't think about what the frogs might have preferred (and we were sure our pond was better (it was about 1/10 of the size and had no fish and was made with water from our taps, had no pond life...but in our 7 or 8 year old minds we through we were doing a really good thing...(and yes we'd sneak into the school playground after hours to take the frogs at the time) 3. Regularly me and my friend would take to our bikes and cycle around the place. We'd have a boundary our parents set us which was pretty much the street, but no one was watching, so we'd cycle for ages outside of our boundary. We were young enough to be snatched and probably naive enough to trust adults offering sweets.... we were very lucky I think! 4. Living near a railway, we'd sometimes throw things over the wall which lead to the track. When I think about the risks...I literally shudder! The trains would be running slowly as it was so close to the station, and this was years ago with the old slam-door trains which are not as automatic as they are now. But the risks... Generally the sorts of things we'd throw would be whatever wound up the other sibling (there were 5 of us, 2 families) it would be something any of us used as a punishment! Nothing major, no bricks but bits of paper, small cuddly toys, CD's, cassette tapes...(I'm showing my age now!) I wouldn't be suprized if this sort of thing happens now but hope that CCTV and better rail systems could feed back a track blockage There were probably others- I can't think of any now but I know that we were generally "good" kids, there were kids I was at school with who were very mixed up, had all sorts of antisocial behaviours (I mean like really risky stuff like bottling each other (as in glass bottles) attempting to near suffocate each other to get "high", smoking at 4 or 5 years old (yes really!) and some pretty major cause for alarm bells. I think the social norms were different in the '80s depending on where you grew up. I think we were left to our own devices and that being seen as a good thing. I mean; in some ways it was. We learned a lot, we developed far more creativity to entertain ourselves (this was before the days of phones and the internet and when batteries ran out for the tape recorder and we'd be waiting ages for a replacement! Kids TV was good and in some cases I'd say better as it felt more unique and not all the same, but it was only on an hour and a half week days, term time, Saturday mornings kicked in eventually but it was only a narrow slot in the morning and once it was gone, it was sports/gardening/nothing interesting to a small child. We were so much at risk and if parents really knew what we had gotten up to when we were left to our own devices, they'd have stopped us being anywhere unsupervised!