Hi! I need to know, how to make my pet's treasure bigger? :D

In the Millionaire Center (here), you will find this item It increases your pet's TC by 1-3 spaces. Other than that, there's a random event where your pet's treasure grows by a space, but it must be pretty rare because I hardly ever get it. :3

Thank you :)

also, there's a [item2=Multi-Compartment Keepsake Box] available from the Cash Shop (or possibly from other users in their shop). This item will give you 10-15 spaces.

Additionally, if you're willing to risk it, the Ultimate Pet Zapper has a chance to give you an increase in TC slots.