More Super Mario AU headcanons, this time of some of the animal friends I'm calling Companion species! I'll get more in detail below! :]
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1) The first image is the in-AU designs for the main-gang's buddies!
I know its mainly because Mario is the main character and therefore needs a trusty steed of sorts, I.E Yoshi, but there are times where I wished Luigi and Peach had their own buddies, so thats exactly what I did here! Birdetta is Peachs companion, Peppers is Luigis, and of course Yoshi is Marios. uwu
Yoshi follows Mario around and joins him on his adventures, thereby making him a Spec-Op of the Mushroom Kingdom as well. Long story short hes essentially Marios partner; he watches his friends back just as Mario does his!
Birdetta met Peach when they were both youngsters, with Birdettas mother having worked in the castle kitchens. The two became good buds and would play all around the castle, something Peach remembers very fondly because at the time she didnt really have many friends. In fact, Peach would probably say Birdetta was the first legitimate friend shes ever made, Daisy the second. Today, Birdetta aids Peach as a royal messenger, where its her job to run throughout the kingdom to deliver important documents between jarls. Shes exceptionally good at her job due to her speed, and sometimes have been tasked with getting messages to neighboring kingdoms.
She and Yoshi are mates. 
Peppers met the brothers through Yoshi, since she was in a neighboring tribe and often came to Yoshis tribe to play. She accompanied the boys when they all made the decision to travel to Mushroom Kingdom, and when Luigi first opened his bakery Peppers was adamant about working in it, so it was pretty much a natural progression since they were already roommates. 
2) So, when I discovered that an Shibe Nintendog made a canonically appearance in Super Mario Odyssey I just had to incorporate them into the AU!
I'd like ya'll to meet Nin, the private detective of Metro Kingdom! He isn't technically a CASO (Convention Alliance Special Operations) affiliate but he works closely with the organization, often tasked with investigating disappearances they can't actively work with. This happens often enough due to CASO agents often being tasked with confronting Pirates, so Nin often has his paws full!
He's rather serious and very good at his job; he's got a nose that can track anyone on the coldest of trails! But don't let his severe look fool ya; he's a complete sucker for scritches and as embarrassing as it might be, he loves a good game of fetch. uwu
As for his species, he's a Nintendog!
3) Speaking of Nintendogs... this drawing is general design concepts for them! Nintendogs are highly evolved animals that look a lot like our dogs but they are generally larger, and have evolved to be able to stand (and move around) on their back legs. They are simple-minded creatures however they are rather intelligent with a level of sapience to them, and like Yoshis they have their own native island, way of living, and culture.
FUNFACTS and LORE BITS:
-While were on the topic, please have some headcanon regarding Companions and how they work:
Companions are animals with human-level intelligence. This generally means that while they dont necessarily have their own kingdoms, they usually reside in simplistic societies with clear structure and culture, and as such they are considered sapient. Companions typically arent able to speak (or if they do, its extremely limited due to their vocal range) but can very clearly communicate regardless through other means, whether it be through universal form of Sign Language or some other way.
They got the name companion since in general terms they are friendly and are sometimes known to have families to host them when they travel into much larger, much more modern cities and towns. As such there were laws put in place to make sure the hosting families did not treat these beings as pets or even live-in servants, something I can imagine being an issue before the World Convention was formed. As time went on, the Convention had begun a program where companion races can petition to be recognized as a Kingdom and join their ranks. The requirements of such include having one or more Sponsor kingdoms, their own land/island, and clearly having an established body of government of some form (that is in some ways democratic in nature).
The very first companion race to have done this are the Kongs and the Kremlings, in which they were officially named a kingdom under the name D.K Isle.
Other companion races include Birdos, Yoshis, Rexes, and Nintendogs.
-Pets are animals who do not hold human-level intelligence and are, typically, domesticated from their much more feral counterparts for a variety of purposes. Sometimes its for companionship, sometimes for livestock, beasts of burden, whatever it may be. These animals include Spinies, Buzzy Beetles, Reznors, Poochies, Dhino-Rhinos, so on.
-Nintendogs come in wide array of sizes, but basic classification is: Small, Medium, Large, Giant. The smallest breed of Nintendogs stands about the same height as a Toad, whereas the Giant breeds can be as large as your average human man.
-Nintendogs cannot speak despite their intelligence and so communicate with others outside their kind in two separate ways: one is a modified form of sign language, given their paws aren't as dexterous as hands despite them having flexible dewclaws. The second is through a very simplified code language, "Woofish", which consists of a small series of barks, growls, and chuffs to cover basic language necessities, things like "yes, no, hello, goodbye" and so on.
-The Yoshi species full name is "Yoshisaur"! They get the name from the strange "language" they speak, with one such sounds they make sounding a lot like "Yoshi". In their way of speak, it roughly means "Hello, friend!" :]
-Yoshisaurs typically name themselves after their favorite foods, and very often their favorite foods correspond to their scale colors! This is where you get names like Melon, Strawberry, Potato, Banana... you get it. xD "Yoshi" the individual isn't actually named that, but he allows Mario and friends to call him that anyway. :]
-Much like Yoshis, Birdos are "Birdosaurs". They're feathered reptiles that are rather similar to Yoshis!
-Their bow-like crest is rather flexible and almost act as if they were ears. They often use them to emote.
But ye! Hope you enjoyed this headcanon blurb! Feel free to ask questions and more to come soon 
More to come soon! ^.^
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