Browsing our new book (did we mention it … ? Oh, we did), I was reminded of the genesis of the above cartoon, and it struck me as an interesting example of the journey we sometimes go on as cartoonists — in search of a joke, or the best way to tell a joke.

In one of our monday morning meetings, back in May 2009, Pascal suggested we might do a cartoon about the idea that the moon is made of cheese. What would mice do with this piece of misinformation, he wondered. As we talked I drew a sketch based on his idea, of two mice pondering their next move.

I can't remember the precise details of how we got from that sketch to the cartoon that got printed, but it's a pretty long journey, I think you'll agree. The final cartoon is set several million years after the scene in the sketch, when mice have evolved to the point where they have achieved moused space flight, and set off en masse to their promised land.

I still like the joke in the sketch, maybe we could have run with that — but we decided that taking the end of the story and looking back left that little gap for the reader to fill in, which is always worth striving for.

In fact, in some ways, the subtext of the final printed cartoon is that first spark of inspiration; the idea that at some point, mice decided it might be worth finding out.

Where we humans fit in to the picture is another matter. Presumably, at some point on their evolutionary journey, the mice kill us all off so they can take over the running of NASA — Mouston, we have a problem. JB