I can confirm that even a 1-by-1 Lego brick can withstand the full weight of an adult human male at 2 in the morning.

...my foot on the other-hand...

Your logic is off, smaller pieces are generally harder to break than larger ones

Yup, the 2x2 can hold 950lbs: https://news.ycombinator.com/item?id=4870283

We can also observe this (to a lesser degree) when they build two story Lego statues like at the Mall of America.

I'll admit I've never seen a huge Duplo statue, but I assume the load limits are similar.

Does lego piece strength vary throughout the day?

If we're getting technical, the weight of a human does vary throughout the day. Generally, while asleep, your mass decreases. You're always gradually losing mass as you inhale O2 and exhale CO2. You're also losing mass as you exhale moisture, and you may also sweat.

Thus an adult human male (who sleeps, say, 10pm to 6am) is less likely to break a lego brick at 2am than at midnight and more likely than at 4am.

When I weigh myself, I make sure to do it in the morning. Too depressing otherwise.

"We can say there is at least one cow in Scotland, of which at least one side appears to be brown."

https://stepinmath.wordpress.com/2016/08/27/logic-with-the-c...

Strength I don't know. Pointiness does for sure.

Perhaps. Plastic structural rigidity varies with twmperature. Temperatures fluctuate throughout the day. This natural variation is probably insignificant in most cases though.

It was a joke about stepping on one of my kids' legos in the middle of the night while half asleep.

I managed to bend a Duplo track as a schild, the puzzle piece connecting them specifically.

A quick but incomplete algo is to ensure an even number of curves and straights. With them even, a bent track needs to be very bent so as to be immediately obvious.

In the picture in the story, the light gray pieces seem like Duplo ones and dark is the "duple compatible" from amazon.

Not really, I have similar or actually probably same sets (and same 'topics' to think about with various bridges and tunnels, track splits etc). I also have these straight or curved stuff in light and darker gray. Cheap non-original stuff is easy to spot - it simply doesn't fit nor hold as well. It doesn't matter whether its bricks or different stuff.

Due to economy of scales, Lego can manufacture those at consistently high quality and relatively reasonable prices. Competition aiming for same quality would be at least similarly priced. Also, its incredibly sturdy. So far I haven't seen a single one crack or break in past 2 years. My kids are not psychos but they for sure have no idea yet about treating their toys with care.