Much like the different Gospels (which all cover the life of Jesus, as told through different eyes), Super Book and The Flying House are versions of the same event. At some point, two kids (a boy and a girl) get access to a time machine, and along with their robot buddy go exploring various events of The Bible. Over time, their names and exact method of travel was lost, so they were called Chris/Joy/Gizmo in Super Book and Justin/Angie/SIR in The Flying House. (Corkey was made up, or forgotten in Super Book)
Which explains the examples under Hitler's Time Travel Exemption Act, as well as why none of the characters in the past are curious, hostile, or unnerved out by the sight of two kids in their modern clothes as well as a robot. This way, the temporal issues that come with with Time Travel are averted.