One of the Visual Philosophy for Children scenes in our book "Cruelty Bites" features an alien zoo exhibiting earthlings -including a human-.
This alone always leads to a rich and lively discussion, but you can make it even richer by pairing it with actual photographs and stories of humans in zoos and 'exhibitions' from the 19th and early 20th centuries.
The above photograph shows Ota Benga, a pygmy who was exhibited in the Bronx Zoo for two weeks in September 1906 in the Apes cage. This was how The New York Times reported it.
This other picture shows a small girl from Congo, on show and possibly being fed at Expo 1958, Brussel's World Fair, as part of the Congolese 'village' on display.
How's that for a prompt for discussion?