Yesterday Caleb announced that when he grows up, he wants to be a Time Machine Maker, so he can travel back and forth through time. Colin advised him that he could be an Inventor, who would invent lots of things, including time machines. Caleb agreed that sounded better than Time Machine Maker.
I love the seriousness of child's play and imagination.
Postscript - today Caleb wants to be Batman when he grows up. I guess we should wait another decade or two to see where things settle.