Pet Simulator 99 Egg Stacking was introduced in Update 99 on October 24, 2026, allowing previously separate eggs, including Exclusive Eggs, to combine into stacks. Stacking works in your inventory, direct trades and Trading Booths. Booths also now hold up to 50 listings in a grid, and buyers can purchase several eggs from one stacked listing.
If your inventory is full of identical eggs, this should be a welcome change. You can handle them as a quantity instead of juggling individual entries. The only slightly confusing bit is that the 50-listing booth limit counts offers, not eggs, so here’s how the two improvements work together.
How Pet Simulator 99 Egg Stacking works
Before Update 99, some egg items were kept separate even when you owned several of the same type. BIG Games says previously non-stacking eggs, such as Exclusive Eggs, now stack together. The Pet Simulator 99 Egg Stacking feature applies in three places: your Items inventory, exchanges with another player and Trading Booth offers.
So if you have a collection of matching Exclusive Eggs, you should see them grouped by quantity instead of scattered throughout your items. They’re still eggs you own, not a new combined egg with different contents. BIG Games hasn’t published a maximum stack size, so check the actual quantity shown in your inventory rather than relying on a made-up cap.
Trading Booth changes in Update 99
The second part of Pet Simulator 99 Egg Stacking is the refreshed Trading Booth. A booth now holds up to 50 listings, laid out in a new grid view. Those 50 are separate listings, not a maximum of 50 eggs. Because one listed stack can contain multiple eggs, the quantity of eggs offered may be higher than the number of listings shown.
Say you’re selling several of the same Exclusive Egg. Before the patch, separate items could make a booth look crowded; now one stacked listing can carry multiple eggs, leaving more of your 50 listing slots free. Buyers can purchase several eggs from that listing instead of going back through a separate offer each time.
Pet Simulator 99 Egg Stacking doesn’t automatically tell you whether a particular offer is good value. BIG Games hasn’t announced new fixed egg prices, transaction fees or a universal stacking limit. Check exactly what the booth says you’re selling and the quantities selected by a buyer.
Can buyers purchase several eggs from one listing?
Yes. BIG Games explicitly confirms that shoppers can buy multiple eggs from a stacked booth listing. With Pet Simulator 99 Egg Stacking, a seller can display a quantity through one offer and a buyer can purchase more than one item from that offer. The announcement does not give an exact maximum quantity per purchase, so check the number displayed in the live trade screen.
In direct player trades, stacks are supported as well. As with any trade, check the egg type and the number offered before accepting. A stack quantity and a listing count measure different things: one describes how many matching eggs are being handled, while the other is how many offers occupy the booth’s 50 slots.
Does Pet Simulator 99 Egg Stacking affect other items?
The confirmed change relates to eggs that previously didn’t stack. Update 99 separately adds new Trading Terminal filters for variants and sizes, an item Favourite action, and trade support for Shiny Fruits, Garden Units and Garden Seeds. Those are distinct improvements. The announcement doesn’t claim every pet or unrelated inventory item becomes stackable or that any egg’s hatch odds have changed.
Egg collectors will also notice the update’s inventory improvements: categories can be collapsed, up to 50 items pinned and sort or grid preferences saved. These make it easier to find what you’re selling, but they don’t change how the Pet Simulator 99 Egg Stacking mechanic works in a trade.
What to check before selling or buying eggs
Start by opening your inventory and looking for eggs that now appear together. When you put a stack in your booth, double-check the egg name and quantity, then look at how many of your 50 listing slots are occupied. As a buyer, remember that a listing can represent more than one egg: review the quantity you’re buying and the displayed price before you confirm. Those few checks are particularly worthwhile now that bulk egg sales are easier.
The Pet Simulator 99 Egg Stacking overhaul is a quality-of-life improvement, not a promise of better egg rewards. For the separate limited pets introduced on Diamond Mountain, see our Diamond Mountain walkthrough, Abominable Yeti rewards and Secret Trails guide. Our Update 98 overview explains that expansion.
Related Guides
Official source: BIG Games Update 99: PSX Classic! (October 24, 2026).
