Or, you could use more Legos.

Today, Matthew built what appeared to me to be a tower of Legos.  "It's a trophy," he explained.

"Neat! Let's build some more trophies!" I said.

"Ummmm, we would have to have 'sssss,'" he said.

"What?"

"'Sssss.'  You have to add an 's' to the end if you want 'trophies.'"