Grandmother and grandson returning from an outing ...
Grandmother: That was very interesting about climate change and the Ice Age. So, who is the one person we need to make sure we look after the planet then?
Grandson: Grandma, we need three people ... Batman, Superman, and Wonder Woman
Grandmother: But there is one other person we need to make sure we look after our plant. Who do you think that might be?
Grandson: Oh yeah ... Spiderman!