What constitutes a novelty gun?
To me it's one that couldn't easily be carried, or aimed and fired.
I consider the old Snake Charmer single barrel .410 shotgun a novelty gun.
I like a short, handy gun but the stock on the Snake Charmer was too short to shoot from the shoulder and the stock seemed to like it would be flimsy.
My $0.02.
I bought a Snake Charmer, when my son turned 7. Fit him perfect and let him shoot squirrel, rabbit, frogs, snakes.
Sold it to my buddy, when his son turned 7.
Bought it back and it has gone through 12 grandkids.
I guess it is a novelty, but we love it.