We found a bunch of pupae when we were working up the garden, so we decided to hatch them and see what they would turn into. We kept them in a jar for several weeks. Finally a big fat grey-brown moth hatched out of one a couple days ago. Two more hatched this morning. We let them go outside.
I'm still not sure what kind of moth they are, but it hardly matters. The important thing is that Conan got to watch a fascinating natural process up close, and loved it.
Update 5/28: Another one hatched this morning!