GPX+ implements a rarity system that makes certain Pokémon eggs more easily encountered than others. Similar to the video games, this system is set in place to encourage players to hunt for more valuable Pokémon in the lab, or engage in Pokémon Breeding to share already-obtained Pokémon with other users. In this way, users must expend a bit more effort to obtain rarer and more sought-after Pokémon and complete their Pokédexes.
GPX+ currently implements five rarities: Common, Uncommon, Rare, Very Rare, and Novelty. The first four tend to reflect the rarities of Pokémon found in the video games, also called 'canon' Pokémon on GPX+. The latter corresponds to the unofficial Novelty Pokémon created by the staff and contributors of GPX+.
A Pokémon's rarity is reflected in how often its egg is spawned in the Lab or created through Breeding; the more common the rarity, the more likely it will appear in either the Lab or the Daycare Center. In this way, Novelty Pokémon also have a "secondary" rarity that reflects how often the Pokémon's non-novelty form, if any, will be generated in the Daycare Center, according to the rules of Breeding implemented in GPX+.
The Common rarity currently contains 426 Pokémon and 174 eggs, the most of the five categories. Pokémon in this category tend to be found in abundance in the games; examples include the "starting birds and rodents" such as Pidgey and Patrat. Common Pokémon will appear most frequently in the lab, and when breeding, will produce eggs more often if paired with an Uncommon or Rare Pokémon. Common/Common pairs also produce the greatest number of eggs.
On the Pokétch and Pokédex, the Common rarity is symbolized by a Pokéball icon.
- Main article: Ditto
Currently classified as a Common Pokémon, Ditto was once classified as Rare, and is to date the only canon Pokémon whose rarity was changed. Despite this, it is one of the more sought-after Pokémon on the site, desired for its ability to breed with any other non-Very Rare Pokémon. Consequently, it's appearances in the Lab are brief; it was once rumored that, in order to curb hoarding, once its Egg and Pokédex entries had been obtained, it could not be found in the Lab or Egg Shelter again, though this has since been disproven by users. Instead of stalking the Lab or Shelter to try and find one, users can partake in the Transforming the Heart exploration, which awards a Ditto egg once completed.
The Uncommon rarity is the "middle-of-the-road" class, containing 250 Pokémon and 139 eggs. From this, it is evident that many single- and double-stage Pokémon are placed in this category. These Pokémon are a bit more scarce in the Pokémon games when compared to the Common Pokémon. Examples here include the Fossil Pokémon and some "paired/trioed" Pokémon like Pinsir/Scyther and Jynx/Electabuzz/Magmar. Uncommon Pokémon will appear a bit more scarcely in the lab when compared to Common Pokémon, and will be produced more often when paired with a Rare Pokémon in the Daycare Center.
On the Pokétch and Pokédex, the Uncommon rarity is symbolized by a Great Ball icon.
- Main article: Unown
All 28 Unown are present in GPX+, each with their own Dex entries, and are classified as Uncommon. However, like Ditto, they are also highly sought-after; all Unown share the same Egg description, so their appearance in the lab is often brief as users attempt to fill their Pokédexes. Their inability to breed makes their scarcity that much more prominent. The Mystery Creature of the Ruins exploration awards one random Unown from those that the user does not yet have an Egg Dex entry; otherwise it will award one of the 28 Unown eggs randomly.
238 Pokémon and their 83 eggs constitute the Rare rarity class, the second smallest group among the canon Pokémon. This group contains many one-off or very hard-to-find Pokémon from the video games; often, they are encountered only in in-game trades or under special circumstances. Examples include the Starter Pokémon such as Bulbasaur or Chimchar, the "pseudo-legendaries" such as Dratini or Beldum, and Eevee and its family. These Pokémon are not produced very often in the lab, and so they tend to be picked up quickly when they appear.
A special case here is Phione. Although it is related to Manaphy, a Very Rare Pokémon, and in many video game sources is labeled a Legendary Pokémon, Phione is classified as a Rare Pokémon. Thus, it can appear in the Lab with the same frequency as any other Rare Pokémon, and follows the same breeding rules as other Rare Pokémon.
On the Pokétch and Pokédex, the Rare rarity is symbolized by an Ultra Ball icon.
Very Rare Pokémon
- Main article: Very Rare Pokémon
The Very Rare rarity class is the smallest of the canon Pokémon classes, with 122 Pokémon and 71 eggs. This group is entirely made up of the "Legendary" Pokémon and their different forms, with each of Deoxys' forms having its own egg entry. Much like in the games, special circumstances allow users to obtain these eggs, be they Events or Explorations. Thirteen of these Pokémon can also be obtained by using Summoning Items to call their egg to the lab, after which the user must look for it and click it to bring it to their party. Like all canon Pokémon, these CAN appear in the lab, but with such infrequency that users are encouraged not to "camp" the lab to find them. Much like the Legendary Pokémon in the games, none of the Very Rare Pokémon can breed, except for Manaphy, who produces Phione eggs only. Professor Cypress' Mew and Ditto may also produce Very Rare eggs on occasion, which are then released to the Shelter as usual.
On the Pokétch and Pokédex, the Very Rare rarity is symbolized by a Master Ball icon.
- Main article: Arceus
The Alpha Pokémon is awarded special status on GPX+, as it can only be obtained in the lab (appearing even more infrequently than other Very Rare eggs) or through special vouchers awarded to contest winners. To date, at least 13 are known to exist on the site.
- Main article: Novelty Pokémon
Novelty Pokémon are special non-canon Pokémon given away during certain events or Explorations on GPX+. These Pokémon are based on various concepts from the Pokémon franchise or wholly conceived by the staff; consequently, this rarity's size is always growing, with 91 eggs and 212 different Pokémon currently occupying it. Novelties based on canon Pokémon are normally either a recolor of an existing sprite or a custom sprite designed for the site. Most Novelties are breedable, allowing users who missed them on initial distribution to hopefully obtain one from the Shelter; in this situation, a "secondary" rarity, matching that of the base, canon Pokémon, is used to determine how often eggs are produced in the Daycare Center. The non-breedable versions are therefore rarer, but can still be obtained during normal play on GPX+.
On the Pokétch and Pokédex, the Novelty rarity is symbolized by a Cherish Ball icon.