“How many eigenstates does the combined system have?”
This SWBQ introduces two non-interacting identical systems with $N$ eigenstates each, and asks students to determine whether the new system will be extensive or intensive.
Students answer $N$ or $2N$. Using spin 1 system, ask for what the eigenstates of two spin-1 particles are. Soon we realize that it's $N^{(2)}=N^2$, which means it's neither extensive nor intensive.