Impossible Animals Pen Upgrades

Upgrading the pen is an official core feature of Impossible Animals: the game's How to Play list includes "⬆️ Upgrade your pen and treadmill to grow your collection." In actual play, the upgrade first appears as an on-screen prompt telling you to level up the pen — documented shortly after your second fusion — and you perform the level-up straight from that prompt. The stated purpose is to grow your collection, and the collection matters because hybrids kept in your pen earn money.

That is also the honest limit of what's confirmed: no official page or gameplay footage shows a cost, a currency, a purchase menu, or named pen upgrade tiers, and nothing confirms exactly what mechanically changes after you level the pen up. Here is what is known and how to use it.

Where you actually upgrade the pen

The documented route is a tutorial prompt, not a shop menu:

1. Fuse until the prompt appears. In the documented early-game session, it arrived after the player created a second fusion (warthog + T-Rex = the "Warth-Rex") and had two hybrids saved. Keep making fusions through the opening flow — the how to fuse hybrids guide covers the basics.
2. Recognize the prompt. The game "is asking us now to level up the pen," as the player describes it — and he identifies the pen as "the terrain here," the ground area where your hybrids live. When the on-screen guidance points at your pen and asks you to level it up, that is the upgrade moment.
3. Act on the prompt. The player simply says "I'm going to level it up" and performs the level-up right there. That prompted action is the only documented way to reach the pen upgrade; no button path or menu for buying it separately is shown anywhere.
4. Know what the aftermath looks like. Right after the level-up, a new panel appeared showing "the animals we have." Treat that screen as the visible completion of the step — though even the player asked "what is it?" about it, as explained below.

One caution from the same footage: near the treadmill there is a shopping area, and the player does buy "an upgrade" there — but he immediately admits "I don't know what we can buy," and the entries he can read (double fusion, a camouflage shop, a charm shop, and the Ember spell that increases training level) belong to fusion, cosmetics and training systems. Nothing ties that shop to the pen, so don't go looking there for a labeled pen upgrade button. Follow the prompt.

What the pen upgrade is confirmed to do

Only the purpose is stated officially: "Upgrade your pen and treadmill to grow your collection." Since hybrids sitting in your pen earn money, holding a larger collection is the whole point of the upgrade as the game describes it.

What actually changed on screen is less clear. After "I'm going to level it up," the player saw a new display of his animals and guessed it meant "we can level up the animals too" — but he wasn't sure what it was, and animal leveling is otherwise tied to the treadmill: "I have to get on the treadmill with the animal, right, for it to evolve." So don't assume the pen upgrade grants a specific bonus. What you can rely on is that the level-up can be performed when prompted and its official goal is a bigger collection.

The only measured limit: five hybrids

Later in the same session, the player fused a skeleton with a monkey into a "skeletmonkey" — and the pen refused a sixth occupant: "so you can only put 1 2 3 4 5," he counts, and "The skeletmonkey didn't fit in the pen there." Eggs don't compete for those slots; they stay in their own separate spot.

That 5-hybrid cap is the only pen constraint actually observed on screen, and it is almost certainly what pen upgrades are aimed at — a full pen is exactly the problem you'd want an upgrade to solve. To be clear, that link is inference: nothing states that leveling the pen raises the cap, or by how much per level. Treat extra capacity as the reasonable expectation, not a confirmed number.

How to play around it

• Take the prompt when it comes. It appears early in the opening flow, so accept it rather than hunting for a purchase menu that isn't documented.
• Plan around five slots meanwhile. Until an upgrade demonstrably adds room, assume the pen holds five hybrids. When it's full, new fusions can't be placed — the skeletmonkey had to wait — while eggs are safe in their own area.
• Keep the money coming. Money funds your fusions and progression; the money guide and how to make money fast cover earning, and the codes page tracks any code that goes live.
• Use the space you have. Where the pen is and how to place hybrids in it is covered step by step in the pen guide; this page sticks to upgrading it.
• Don't mix up the two upgrade tracks. The treadmill is its own facility with its own upgrades, and it's what levels up your animals — see how to train hybrids. The pen upgrade concerns the pen and your collection.