Modern Neopets has additional Neopet species that don't appear in the retail version. There are multiple ways to get them, some easier than others.
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Species that are always available
Diregos, Ginkos, Yumacks and Kohmos are available to create at all times, as they're basic Neopets within the site. Like all basic Neopets, you can create them in the red, blue, green, or yellow colors.
Additionally, you can get them in various fun colors by using a morphing potion, magical plushie or transmogrification potion.
Soreens
Soreens were originally an April Fools' fake Neopet TNT put out, later turned into a Petpet in the retail version. They can be created in the Waterfall Sanctuary, which can be accessed from the Pet Central or the Shenkuu map (the spot you have to click is circled). They can be created in the striped, spotted, or speckled colors.
Lulamus
Lulamus are a a bit tricky to get. If you manage to obtain an Old Broken Whistle from Pick Your Own, you can go to Donny's Toy Repair Shop to turn it into a functional Lulamu Whistle. You can use it at the Enchanted Glade, available from the Brightvale map (the spot is circled below) or from the Pet Central.
Tatsus
Tatsus are an old Neopets design that was replaced with the Eyrie. They are rather hard to get, originally released via the Ancient Unearthed Morphing Potions- a custom potion that would turn a pet into a Tatsu of a random color that was given at the Money Tree. Although you can still get an Ancient Unearthed Morphing Potion (either by buying one from a user shop or obtaining one from the Wishing Well), there isn't an «official» way to get a Tatsu yet.
The easiest way to get a Tatsu (or any other Neopet for that matter) right now is with either a Morphing Potion or a magical plushie. With these, you have full knowledge of the color your future Tatsu will be... but it does take a bit of fun away, in our opinion! In case you're curious, Deebs (the artist behind the Tatsus' lore in MN) talked about the probability of each color you can get from an Ancient Unearthed Morphing Potion here:
Moteres
Moteres were introduced to the site on September 13th of 2022, along with a temporary daily activity: interacting with Major Miner, who is located in the Moltaran caves, will grant you a Glowing Moltara Lamp of a random color. Bring the lamp to the Crystal Cave, and you'll be able to get a Motere of the same color as the lamp you picked!
Below are the maps of Moltara- the main map has the entrance to the caves circled, while the map of the caves has Major Miner circled in blue and the Crystal Cave circled in yellow. These locations are also linked in the Pet Central.
Major Miner only offers these lamps from September 13th until September 20th, though you might catch them being sold at Lampwyck's Lights Fantastic year-round.
Kitzens
Kitzens were introduced to the site on February 14th, 2023. Not unlike Krawks, they evolve from a Petpet that can be found at Merifoods through a random event. They're quite rare, though you may get one through the Wishing Well if the rarity cap has been removed.
Afterwards, head to the Mysterious Fountain in Brightvale from the map (circled below) or the Pet Central.
Remember to have a Kitzen attached to your active pet when you want to evolve them from their Petpet form.
Why are they found in Merifoods? Well, according to the announcement, there's some lore...
More information
All species on MN can be gotten with Morphing Potions and magical plushies, which come in a variety of colors, as well as with Transmogrification Potions, which will always result in a Mutant pet.
These items are, generally speaking, a lot more affordable and accessible in MN than in retail Neopets. So, even if you fall out of love with one of your pet's appearance, it's pretty easy to find a new form for them!