Buy Grow a Garden Red Nosed Reindeer
Rudolph is a hidden pet in the Grow a Garden Christmas update. It does not show up in any egg preview or shop listing. You cannot hatch it or buy it in game. It unlocks through a special ritual that needs the sled item and eight Christmas reindeer at level 100. All eight reindeer must be placed in the garden, not in storage, for the sled to count them.
Rudolph works as an XP engine for your whole account. Every 4 minutes, it grants 2,000 experience to a random non-reindeer pet in the garden for every reindeer on the field. With eight reindeer, that is 16,000 XP per cycle. Placing only one to three pets you want to level makes the random targeting focus on them.
Rudolph also mutates fruit. Every 15 minutes, it applies the Ornate mutation to a number of fruits equal to the reindeer in your garden. With eight reindeer, up to eight fruits get Ornate every 15 minutes.
Both skills scale with the reindeer you keep active, so your reindeer stay useful after the unlock. Rudolph is a strong mid to late game reward for any Grow a Garden player.