The carcination phenomenon (animals convergently evolving crablike body plans) is a bit overstated in pop science media. Like, it’s definitely a thing, but mostly among animals that aren’t too distantly related to crabs and face similar environmental pressures. There are a lot of similar examples of convergent evolution that for whatever reason don’t get near as much attention. For example, the analogous phenomenon for mammals would be mustilization - many mammal species convergentky evolving to be more weasel-like.