According to science (and internet memes), all species are destined to eventually evolve into crabs. This is the process known as 'carcinization', and it's also the title of a new Dungeons and Dragons homebrew by Sireacquired. This supplement reimagines the most popular DnD races and monsters as crab hybrids, with new stats and crabby abilities to match.
This isn't the most powerful set of optional rules for your character. Firstly, the homebrew is designed for the 2014 version of D&D 5e, so it hasn't accounted for the many power upgrades found in the newer core rules. Secondly, most of the species can only buff your character's physical stats, which limits their build options. And lastly, there are more than a few underwhelming species abilities - like the Crab Dwarf's magical power of altering their buoyancy "to sink up to 250 feet in water at the start of each of your turns".
It may not be the most balanced homebrew, but I'd recommend giving it a read anyway. That's because it's delightfully funny. Sireacquired paints a brilliant mental picture of a fantasy D&D world post-crab, with lines like:
"Due to the rarity of crab dragonborn, those born to two crab dragonborn parents are few and far between, but are generally considered most delicious when steamed and served with butter and lemon."
"Picture a small creature, mischievous but not necessarily malicious, darting from cover to cover in the smallest cracks and crevices. Is this creature a crab or is it a goblin? It is both; it is a crab goblin."
The homebrew crab-ifies 10 species: Aasimar, Dragonborn, Dwarf, Elf, Gnome, Goblin, Halfling, Human, Orc, and Tiefling. Their special abilities closely resemble those originally designed by Wizards of the Coast, but there are plenty of new and unusual crabby options, too.
Carcinization also features stat blocks for 12 monsters that have undergone the same evolutions as the playable species. These include the mighty Owlbearcrab (because combining two animals wasn't enough), the Displacer Crab, the Phase Crab, and the Ooze Crab, which was apparently created after a culinary experiment gone wrong.
You can find the full homebrew here. If you'd like to chat about crab-themed character builds, then hit us up in the Wargamer Discord.