Friendly monsters

In Final Fantasy IX, there is a group of Friendly Enemies the party may encounter on the World Map. The player will know when they have encountered one from the battle music, which is much more cheery and sweet than the normal battle music. The Friendly Enemies request a jewel and in return give the party a large amount of AP.

For this reason, it is best advised to encounter these monsters when a character needs to master a certain skill, although these encounters are random. If the player encounters one of the Friendly Enemies does not want to master a certain skill, one can attack it to make it run away. Then, the player can find it again when they have a skill to learn.

Types
The order of Friendly Creatures above is the order the player would find (or be able to satisfy the requests of) them in the game when playing through the main quest. It, however, does not have to be completed in this order. As long as all eight have been encountered previously, the Friendly Yan encounter should be a success.

If the other eight Friendly Enemies have not been encountered and pleased with their requested gems, Yan will ask the party, "Have you met the others?" before running away. Caution must be taken when searching for Yan because its less-than-friendly cousins are quite powerful. Yan wants the Diamond obtained from the Garuda.

After finding all nine Friendly Enemies, Yan will say, "Thanks a lot! Now you can reach the round guy!". This means Ozma can now be hit with physical attacks. Additionally, Ozma will be weak to shadow-elemental attacks instead of absorbing them.

Gimme Cat
Outside Daguerreo and its surrounding islands, the player might run into a Gimme Cat that requests the player give it a Diamond. Gimme Cat, however, is not part of the Friendly Enemies sidequest, and will give nothing in return if given a Diamond.