Adopt Me Pets & Aging Guide
Pets go Newborn → Junior → Pre-Teen → Teen → Post-Teen → Full Grown while equipped. Commons take fewer tasks; Legendaries take many more. Four Full Grown of the same species make a Neon at the Neon Cave. Four Neons make a Mega Neon.
Eggs
Starter Egg is free (Cat or Dog). Nursery stock includes Cracked, Pet, and Royal eggs plus event eggs. Higher eggs have better Legendary odds, still low. Event pets are often the real value.
Aging
Keep the pet equipped and clear its needs. Community numbers put Commons around ~25 tasks to Full Grown and Legendaries near ~183. The Pet Pen can age extras passively while you are online.
Neon and Mega
Neon Cave wants four Full Grown copies of the same pet. Four Neons fuse into a Mega Neon. Age before you fuse or trade — Newborns of the same species are worth less.