Secret nametag that lock mobs in baby version

The kitties, wolves cubs, the baby dolphins are so cute and adorable, but unfortunately they grow up so fast. My idea is create a nametag like the others one that already exist (like "toast", "johnny", "jeb_") that locks the mobs in baby version or turn adults mobs in baby version again and lock too, but offcourse, only mobs that has baby version. The names that I suggest (can be only one or more, like "Dinnerbone"/"Grumm" ) is "Saint" that is my lastname, "Everstone" (reference about Pokémon's stone that locks evolution) or another one. Thx a lot.