On the subject of light comedy

The DUG regards Fletch as a light comedy which does not have a complete story form, and, being a light comedy, a complete story form is not expected. Even though Arsenic and Old lace and Bringing up Baby have complete story forms, are they not light comedies. If not, what is their class of comedy

Not sure if sub-genre is the same thing you’re referring to as class, but Arsenic and Old Lace is a farce. I haven’t seen Bringing Up Baby, but know it’s been referred to as screwball. Screwball and farce tend to overlap at times (you’ll see Arsenic and Old Lace referred to as a screwball as well), but that’s typically because farce entails a broad spectrum of comedy styles.