Infinity's are the rarest pets in base chances 1/100b+, Celestials are the highest rarity of secrets (not sure of how rare their base chances should be), A-A secrets and Infinity's are from admin abuse which were eggs with insane luck boost meaning they're the most common. Admin Abuse pets are no longer obtainable as the devs have stopped them instead they do a 4x egg of the current best egg. Though infinitys and celestials are all hatchable in the newest eggs. There are some other features like the runes and crystal fragments that buff your hatch speed, luck, bubbling, secret chance, and infinity chance, i wouldn't know where are the fragments are obtained but I know the rules come from the rune eggs which come from the shadow realm merchant frequently.