Re: " toughest substance in the known universe"
The early Lego bricks were almost exclusively just red and white, no yellow, black or grey. The bases were a cream colour, and instead of a circle pattern to lock the 'knobs' of the bricks in, used to have square holes in the bottom that the 'knobs' would fit in. Additionally, the 2x1, 6x1 and 10x1 narrow bricks would not have pins to help hold them on, but had cross-wise narrow divisions to help keep the sides in enough to grab the knobs of the lower bricks. It did not work as well, and often a complex model would be difficult to build because it just would not lock together.
The plastic of Lego from 50 years ago is different to modern bricks, and I think it was a styrene based plastic, and a bit brittle (yes, I am talking real Lego here, not the Betta Bilda and like copies, which we also had). Consequently, it would break on occasion. My older brother and I used to build models, and then use the spring powered suction dart guns (with the suckers removed - never be allowed these days) to 'blow' the models up, in scenes reminiscent of Stingray and Thunderbirds. Every now and then, we would break a brick. (Side note. In the film Thunderbirds Are Go, some of the houses that Zero-X crashes into are clearly made from Lego if you frame step the DVD!)
There used to be completely different windows and doors, with glazing in as well. I remember the garage bases with up-and-over doors, which were the right size to allow you to build a garage for a Matchbox sized car. The garage door auto-opened (it was weighted) and was held down by a flap that caught the bottom of the door. 'Drive' a car up, and over the flap to press it down, and the door would open. Push the car in, and close the door, and then trigger the door, and the car would roll out because it parked on a shallow ramp that formed the base of the garage.
Originally, the roof bricks were steep, almost 45 degrees so that a 2x4 roof brick had 1x4 knobs on the top to allow you to build the roof.
There also were wheel bricks, with wheels with rubber tyres (originally white/beige, but replaced quite quickly with black tyres) that had metal pins that would push into the wheel brick. If you stood on on one of the wheels which was pin-up, you really know about that! This was extended to train tracks and special flanged wheels (we originally used the wheels with the tyres taken off), complete with electric motors.
Things started getting different in about 1968, with different plastic, curved bricks, and specialist fence, trees, flowers and less steeply raked roof bricks, with additional colours and clear bricks, different plastic, and more brick sizes. And then they introduced models with special parts made only for a particular model, which would always go missing. People started building the models and leaving them built, rather than using their own imagination.
My youngest son, who is 18, has his complete lifetime's worth of bricks from special models (he's a real Lego fiend). We've just done a tidy and consolidation, and we have many thousands of bricks, filling all the drawers of a desk, along with storage tubs of the more common bricks, and glass coffee jars for the more specialist bricks. I don't reckon he could make any of the models up now, but he has vowed to find all the bits for the X-Wing kit he had! We may have to go to the Lego site and order a piece or two (yes, they sell single bricks from almost everything they've done in the last 20 years, but they tend to be expensive). They will even print on bricks (particularly body parts) from your own design if you are prepared to pay for it!
And I'm about to take ownership of the remains of my Lego set from the 60's from my father.