Mash the banana in a small bowl until mostly smooth.
Whisk the sugar into the whole milk until fully dissolved. Add the heavy cream, vanilla, salt, mashed banana, and pudding mix if using. Whisk until smooth.
Pour into a Ninja Creami pint, staying below the MAX FILL line. Seal with the lid.
Freeze on a level surface for 24 hours.
Remove the lid, place the pint in the outer bowl, attach the paddle to the lid, secure the lid assembly, and lock it onto the motor base. Select ICE CREAM. The base will look crumbly — this is normal.
Add 3 to 4 tablespoons of milk to the pint, reinstall it, and select MILKSHAKE.
If it's thicker than you'd like, add another tablespoon of milk and RE-SPIN.
Pour into a tall glass, top with whipped cream and a cherry, and serve immediately with a straw and a long spoon.