Any Tools for creating NPC's "on the fly"?

Old DM, New to Roll20. I've been looking around trying to find any tools or helpers for making NPC sheets quickly. Both for prepping a small hand-made module as well as for the (Seemingly frequent) occasions of needing to generate an NPC with stats on-the-fly. I haven't really found anything where I can say Add - NPC
Select type : Commoner
Select level: 2
and then save that NPC, with stats to re-use if he ends up coming back in the campaign. 

are there any helpful tools, macros, or 3rd party bits that i could easily import into my roll20 game?

thanks

Something like that would require the use of an API script, which requires a Pro subscription.

Is there an API script to do that?

Which system are you talking about?

For Pathfinder, there's a script called creaturegen which lets you copy/paste text straight from Paizo's NPC gallery.

I also use a macro which outputs whatever's in the red bar
 @{selected|Bar3}

When I need generic mobs in a hurry, I put an attack macro in their red bubble.
  something like this: [[1d20+5]] to hit [[2d6]] damage

For D&D 5e, I think you can drag and drop creatures from the compendium directly.

I also keep a page in my game as a creature gallery where I set up a bunch of tokens ahead of the game. Then I can copy/paste them to the correct page when I need them.

I'm setting up a D&D 5e campaign. And if things go well (my old table-top group) we'll likely continue with future games, so a pro subscription isn't out of the question if it makes my life easier.

I like your idea of a creature page, plexsoup. thank you. That will work for easily getting my pre-made NPC's into the map. I'll explore that compendium drag and drop. I haven't explored that feature yet. Does it have common non-mob NPC's?

Thank you all for the quick help!