A cobblestone generator is supposed to mix a flowing stream of lava with water, by placing a bucket of lava next to it (which creates a reusable, infinite lava source). But Soldier dumped the lava directly into the water, which created a block of obsidian instead and wasted the lava.

I haven't mined the craft for over a decade, but this is the kind of knowledge that lasts for a lifetime.

I'd add to rtxn's comment that the origin of the meme comes from a fan made game mode named "Skyblock". In this gamemode, you only start with a bit of dirt, plants, and a bucket of water and a bucket of lava.

The joke is, if you fail to create a cobblestone generator, you are locked out of most of the progression of the game, and you'd better restart.

It's also really easy to fail a cobblestone generator, so most Minecraft players have experienced this feeling.

And for the Minecraft players here: You don't make the water come to lava. You make the lava come to water.

I did it yesterday. Twice. I have since fixed my problem, and claim I wanted the obsidian as a backdrop to the generator so I don't mine out every block around it.