Oh, Charmander is a Pokémon from the videogame Pokémon. In the video the titular animals evolve into different, stronger animals.
They fight battles and after winning enough of them it triggers their evolution.
The joke is that instead of evolving as they do in the videogame, they instead follow the meme concept of carcinisation and all evolved into a crab shaped Pokémon.
It’s a bit of a horror movie trope, where the protagonist is an ‘other’ and slowly swarmed by a group of identical or similar enough beings.
The implication being that their difference is not wanted and/or that they know too much about the situation which could be a threat, this further ties into the carcinisation joke because everything else has become a crab except for this one child.
You seriously never in any way came into contact with the pokemon series? It’s been huge with kids in the late 90s / 2000s and is still a massive franchise.
