I thought I'd make this tutorial because nobody else has and because I've had some great experiences so far doing animal forts.
Step 1: Go into adventure mode and perferably find the largest sized animal person that can spawn in a dwarven civilization.
(Size is proportional to strength in DF so the one with the largest size will be the most OP)
Step 2: Start a fort as the civ that has the variety of animal person you want.
(If the animal person is from another civ it won't be able to do any labors in your fort or will just be a corpse when you start playing fort mode again for some reason)
Step 3: Retire the fort the time being, go into adventure mode and spawn an adventurer from the animal person species you want.
Step 4: Create a ton of party members also from that species or from others you want in your fort.
(I spent about 2 hours one cozy quarantined morning creating, speccing, and spawing weapons and armor on about 50 party members. Theoretically you can spawn infinite party members but I can't verify that)
Step 5: Start your adventure with your 9035 fully armored elephant seal man swordsman companions huddled around you in a circle and immediately retire.
(protip: Starting your adventurers as rangers automatically gives them better dodging skill)
Step 6: Unretire your fortress and basque in the glory and lag of the announcement screen telling you that over 9000 elephant men have become rangers in your fort.
Step 7: Effortlessly turn the entire world into t̵͖̒ ̸̢͊h̶̺̅ ̷̧͎̃e̵̖͕̎͝ ̶̯̈́̚ ̶͖̂̽s̴̘͝ ̷̢̈́m̸̛͓ ̶̢͉͐e̵͓̦͒́ ̴̺̔l̶͍̲̾ ̶̘͉̇f̶̫͖̌ ̸͕͉̃ ̴̡̥̈́h̸͇̰̎̒ ̷̰͇̈́̇ę̷͓̔ ̴͖̒l̸͎̃ ̷̘͓̽l̸͈͇̊͑ ̷̛͔͑ ̵͉̈́̕ż̵̡͕ ̶̊͜ŏ̶͇̫̆ ̴͍̈́n̵̘͙̓͠ ̸͝ͅȩ̷̯͆ as every known and unknown site in the game becomes an occupied holding of your fort.
Some DFhack commands you may need:
fix-ster fert all
(All your adventurers start out as asexual and therefore unable to spawn babies by default, this command remedies that and also remedies any asexual animals and monsters you have in your fort for some reason)
If your starting a fort with snake men or any egg laying animal people in general you still need to build nest boxes, if you have a species that lays huge clutches of eggs and you want to start hoarding a massive pile from the get go. you can marry them off by finding their ID with.
lua print(dfhack.gui.getSelectedUnit().id)
And pasting it into this command
gui/family-affairs [ whatever number the ID is]
The aforementioned command will bring up a GUI menu ingame where you can marry them off to someone their sexual orientation permits them to.
(PS. you don't have to worry about furfags or scalies because the only options you can choose in the GUI are members of the same species)