
Answers.com contributors have said:
Aug 17, 2011 No, there are only 6 Moshi Monsters to choose from on Moshi Monsters. However, you can collect Moshlings, but the number of Moshlings changes as they continue to add new Moshlings to the Moshi.

The rarest Moshling is Roxy because the code is from mystery notfrom subscribing or buying Buster's Lost Moshlings.
The rarest moshling is Oddie because you need to get it with thecorrect flowers, otherwise you will get Snookums.
It is Mini Ben because you need all the same plant and colorwhich makes it harder.
Big Bad Bill (the voodoo guy) because you need the rarestmoshling seeds.
It is the secret moshlings. Like Roxy, Lady Goo Goo or DustbinBeaver. Or if you are just talking about normal moshlings, it isprobably one of the ones that members can only get, so the rarestmoshling is Cutie-Pie or IGGY.
Oddie is the rarest moshling and hardest moshling to get becauseOddie shares the same flower combination as Snookums. To get Oddieyou need a yellow star blossom, a black star blossom, and a purplestar blossom. Oddie is the doughnut from the foodies set.
Ultra rare moshlings
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077 Waldo the Tabby Nerdicat [Kitty] Pink Love Berries, anyDragon Fruit, Red Star Blossom
078 *Burnie the Fiery Frazzledragon [Beastie] Red Snap Apple,Red Snap Apple, Blue Crazy Daisy
079 Gigi the Magic Mule [Pony] Blue Hot Silly Pepper, Red MoonOrchid, Yellow Hot Silly Pepper
080 *Cleo the Pretty Pyramid [Worldie] Blue Crazy Daisy, PinkCrazy Daisy, Yellow Snap Apple
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082 General Fuzuki the Warrior Wombat [Ninja] Yellow LoveBerries, Purple Star Blossom, Red Hot Silly Pepper
083 Gurgle the Performing Flappasarus [Dino] Red Dragon Fruit,Yellow Magic Beans, Purple Love Berries
084 *Scamp the Froggie Doggie [Puppy] Black Snap Apple, PinkDragon Fruit, Blue Moon Orchid
087 *Shishi the Sneezing Panda [Beastie] Black Crazy Daisy,Yellow Hot Silly Pepper, Red Dragon Fruit
088 Oddie the Sweet Ringy Thingy [Foodie] Yellow Star Blossom,Black Star Blossom, Purple Star Blossom
089 Big Bad Bill the Wooly Blue Hoodoo [Spookie] Yellow LoveBerries, Black Star Blossom, Blue Star Blossom
091 *Cutie Pie the Wheelie YumYum [Foodie] Pink Star Blossom,Blue Dragon Fruit, Purple Crazy Daisy
097 *Mini Ben the Teeny TickTock [Worldie] 3 Black SnapApples
100*^I.G.G.Y. 'I'm Gonna Get Ya!' the Pesky Cursor [Fluffie]Purple Crazy Daisy, Purple Crazy Daisy, Black Moon Orchid

Super ultra rare moshlings
101 Roxy the Precious Prism [Secrets] Ultra Rare: Radiant RoxyRose, any flower, any flower
To get the Radiant Roxy Rose seed, enter HOBBIDIDANCE (in alluppercase) as the secret code on the login screen. This code (likeall other codes) can only be used once. Then plant the Radiant RoxyRose, any seed, any seed.
The code for Roxy the Precious Prism is found in the book,'Moshi Monsters: Moshling Collectors Guide'.
102: *Lady GooGoo the Singing Baby [Secrets] Ultra Rare: SuperMoshi Mission 1: Missing Moshling Egg
103 Blingo the Flashy Fox [Secrets] Ultra Rare
To attract Blingo, you need to enter a secret code when loggingin, which can be found on the last page when you purchase 'Buster'sLost Moshling Book'.
Please be aware this secret code can only be used once.
If you redeem a code successfully, check out your garden seedbag and plant the Hip Hop Hibiscus seed with 2 others to attractthe moshling. When Blingo comes, click on him and press keep, thengo back to your house and check him out.
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105: Wurley the Twirly Tiddlycopter [Techies] Ultra Rare:Mission 2: Voyage Under Potion Ocean
106: Plinky the Squeezy Tinklehuff [Tunies] Ultra Rare: Mission3: Strangeglove From Above
108 **Nipper the Titchy TrundleBot [Techies] Ultra Rare
To attract Nipper, you have to buy the Moshi Monsters: MoshlingZoo game for Nintendo DS. The game comes with a code to get theRobo Dendron seed. Plant the Robo Dendron seed with two other seedsand you will get Nipper.
Note: the code is a one-time use, non-sharable code and can onlybe used once.
109: *CocoLoco the Naughty Nutter [Nutties] Ultra-Rare: Season 2Super Moshi Mission 1: A Close Encounter of the Zoshi Kind