Everyone has a different approach to doing comics. Some people script things out way in advance, others just follow where the inspiration flows. I admit I tend to do a combination of improvisation and pre-planning where the overall storyline is planned out but then I will have parts of the storyline where I just let the characters write themselves. Usually in this method there are key scenes and strips, sort of like little rest stops along a highway where you know things are going to touchdown there and it’s just a matter of getting from point A to point B.
This was one of those comics where the script and joke was something I had in mind way in advance for because it just made me amused every time I thought about it.