I used to think the most dangerous place to leave toy cars would be on the stairs. Now that I have children of my own, I realize that it's actually the bathtub.
You can always trust kids to one-up you like that.
This leads me to a related conclusion at which I also couldn't have arrived without having been a parent. Be brave, this is gonna hurt a little: your kids are smarter than you.
Not just statistically smarter, or better at texting, or whatever it is you routinely tell yourself to help yourself sleep at night, but actually smarter. Sure sure, you can tie your own shoes and snicker at the dirty jokes in the Pixar films that are still going way over their little heads, but otherwise they are floating like butterflies and stinging like bees while you are basically standing around scratching your ass. Intellectually speaking, anyways.
Now to be fair, they have a lot less going on than you do - no work, no responsibilities - but all this means is that they are able to devote 100% of their formidable processing powers to a) obtaining junk food; b) shedding whatever work or responsibilities they are handed; and/or c) formulating "non-linear interpretations" of rules.
Cases in point:
a) We recently saw twin eight-year-old boys at Superstore get the old "One treat, do you hear me? ONE!" from Mom, then - having made artful use of Dad's inattention during the remainder of the shopping trip - waltz out of the store a half-hour later with one of them cradling a family-sized chocolate bar and the other a bag of marshmallows. (Pwned!)
b) My girlfriend finally hit on a potty training incentive that worked: every time her daughter used the potty, she would get a sticker. When she earned ten stickers, she got a trip to the store to pick out one treat, whatever she wanted. Once at the store, she looked her mother straight in the eye and requested a roll of stickers. (PWNED!!)
c) Small Fry. All the time. *sigh* pwned.
And if the three-year-old is running laps around my best efforts I'm thinking I'll probably need to retain a lawyer before Medium Fry hits her teen years, to help me through curfew negotiations.