Frog Song

Frog Song, also known as Pond Chorus, is a Blue magic spell that corresponds to Toad

Final Fantasy IV
In the DS version, Edward can learn Frog Song at a certain level. It can also be used through the Sing Decant Ability as long as the character has it equipped and is at the necessary level.

Final Fantasy V
Frog Song is a Blue Magic spell learned from Toad type enemies.

Final Fantasy VI
Although not one of Strago's Lores, Imp Song is an enemy skill used by Ultros. It turns the entire party into Imps.

Final Fantasy VII
Frog Song is an Enemy Skill learned from the enemies Touch Me, Toxic Frog, and Christopher. In addition to turning one enemy into a Frog, it also puts it to Sleep for a cost of 5 MP.

Due to an error in either the coding or the writing, the spell's description claims it affects all enemies, while it only affects one.

Final Fantasy XI
Frog Song is an enemy ability that is not learnable by Blue Mages. It can be used only by Poroggo and inflicts a Costume status effect, turning the player into a frog, as well as charming them. Some Notorious Monster versions have an upgraded version called Frog Chorus that applies to a group of players.

Final Fantasy Tactics Advance
Animists can learn Frogsong, which inflicts Frog. Lamias can use Poison Frog which inflicts Poison as well as Frog.

Final Fantasy Tactics A2: Grimoire of the Rift
Animists and Lamias retain their Toad-status moves, though the former's move is known as Toad Song.