Poochy: Mario's dinosaur Yoshi's dog
Poochy is the cute adorable dog that helps Yoshi with his adventures. Since the Yoshi series is essentially a spin-off from the Mario series, it can be said they coexist in the same sphere.
The Yoshi-Poochy relationship is fairly similar to the Mario-Yoshi relationship, in that they are sidekicks, but also have some degree of control over each other, almost like a owner-pet relationship.
If Yoshi is Mario's pet, and Poochy is Yoshi's pet, does that make Poochy, Mario's pet's pet? Ok, maybe that's a little crazy but just something interesting to think about it. Perhaps this isn't what Nintendo had in mind. But don't call Yoshi, Mario's pet! Poochy on the other hand, maybe he can be Yoshi's pet. He's not exactly the smartest character in these games.
If there was a chain of command, then perhaps Mario can have control over Poochy as well...
Poochy first appears in Yoshi's Island: Super Mario World 2 on the Super NES. The SMW2 part of the title is a bit of a misnomer, as the Yoshi series is kind of more in their own realm.
It's a little hard to explain the game in terms of the Mario universe as Yoshi's Island is a prequel where Yoshi has to take Baby Mario along with him on the journey to rescue Baby Luigi from Kamek. Future games no longer feature Baby Mario and it is just Yoshi on his own.
Poochy appears in some levels as a companion, once Yoshi jumps onto him, Poochy will move forward in the direction Yoshi is facing, and will become invincible - defeating any enemies in the way. In addition, Poochy is able to walk on hazards such as lava and spikes.
In Yoshi's Story for the N64, Poochy can't be ridden on, instead he will help Yoshi find fruits and hearts. However, Poochy regains his old functionality in Yoshi's New Island for the Nintendo DS and Yoshi's Woolly World for the Wii U and 3DS.
Poochy also has become a lot smarter in Yoshi's Woolly World, he's able to break certain through blocks, give boost Yoshi's jump, and even help with obtaining certain collectibles, delivering them to Yoshi!
In general, Poochy doesn't appear in a lot of levels of the Yoshi games, but In Yoshi's Woolly World scanning a Poochy amiibo will unleash him in any level, or by using a Power Badge that can be purchased by beads.
There's always been a bit of crossover between the Mario and Yoshi series given they are in the same universe, you can see familiar enemies such as Koopa Troopas, Piranha Plants, Bullet Bills, Shy Guys and Cheep Cheeps to name a few.
Poochy on the other hand has stayed exclusively in the realm of Yoshi games and has not appeared in the Super Mario series at all. In fact he hasn't appeared in any spin off games like Mario Kart either.
That is, until in 2017 when he showed up in Super Mario Odyssey. Poochy appears in a number of "hint art" which are pictures of buried Power Moons. Dogs like to bury bones, so perhaps this dog likes to bury moons! Hint art are a major theme in Super Mario Odyssey as there are many different types of hint art to make you go on a scavenger hunt for moons.
In the early parts of Super Mario Odyssey, Poochy was only found in hint art, but later on, he makes a physical appearance as well in Bowser's Kingdom where he can be fished out of the purple poison water using a captured Lakitu.
Unfortunately, Poochy's appearance here is literally a couple seconds, as quickly he morphs into the a Power Moon to be collected by Mario.
Now that Poochy has made an appearance in a Mario game, will we start seeing more of him it the future? The upcoming Super Mario Party seems like a good place for Poochy to show up, given that there will be a large number of playable and non-playable characters that will appear, could Poochy be one of them?