A fairly standard dinner conversation at our house: 
Daughter2 (4 y/o): Sweetcorn is grown like grapes, because they are both juicy. But they are different colours. And their juice tastes different.
Daughter1 (7 y/o): I know how to grow a potato. Put a potato in a bowl, and put no dirt in. And then water it. Then put in a tiny bit of food, which is dirt. And most importantly, keep it safe from greenfly.
Son (5 y/o,  shouting): And dinosaurs!
Daughter1 (7 y/o): They are extinct! They don't exist any more.
Daughter2 (4 y/o): Unicorns still exist. Just on a different planet!
Daughter1 (7 y/o): Yes. Unicornia: the heaven of unicorns. You can't exactly bring yourself to heaven with a teleporter, mostly because heaven doesn't really exist. And God doesn't really exist.
Mammy: Remember, you have to respect other people's opinions on religion too.
Daughter1 (7 y/o): Yes, like the way that you're not allowed to push us off a balcony.