The family went to Costa Rica last year to visit DH's family. I had to stay on for work, so DH was traveling with DS5 alone. (DS9 was traveling with his grandparents.) There's all sorts of paperwork he had to carry to take DS5 out of the country (and back in) with only one parent. Anyway....
They're returning to the US. At passport control the officer checks their passports, and the paperwork. Stands up and peers over the counter at DS5. (who was then 4) "Son, where is your father?" Big eyes. Thoughtful silence. "Who is your father?" Thoughful silence. "Are you traveling with your father?" Thoughtful silence continues. DH is starting to get a bit concerned at this point thinking DS5 is going to come up with "God" or "Heaven". DS5 is thinking too hard. Yet, he knows that he can't look concerned since that will trigger the officer to be concerned. The officer is starting to look a bit frustrated. DH quietly, and calmly says "Try 'Daddy'." "Son, who is your Daddy?" Index finger comes out and points at DH. "Thank you sir, you may go."