ThatOne_Writer

It's the inverse of Chekov's Gun ("If there's a gun on the table in act 1, it should go off in act 3" or someone like that). Asimov's Tail is like saying "If a gun goes off in act 3, it should be on the table in act 1."

You don't need that for guns because we all know what guns are. A character in a modern setting pulling out a gun to win a fight on page 120 isn't going to bother the reader. But a tail is unexpected: You need the reader to buy in to and expect the tail before it becomes plot-relevant, or it'll read like a deus ex machina.

(Another comparison is Chekov was talking about the stage, and Asimov is talking about books. Asimov's Tail may not be as applicable to the stage, where the audience can all clearly see the character's tail in his costume.)

I've been resource gathering for YEARS so now I am going to share my dragons hoard

Floorplanner. Design and furnish a house for you to use for having a consistent background in your comic or anything! Free, you need an account, easy to use, and you can save multiple houses.

Comparing Heights. Input the heights of characters to see what the different is between them. Great for keeping consistency. Free.

Magma. Draw online with friends in real time. Great for practice or hanging out. Free, paid plan available, account preferred.

Smithsonian Open Access. Loads of free images. Free.

SketchDaily. Lots of pose references, massive library, is set on a timer so you can practice quick figure drawing. Free.

SculptGL. A sculpting tool which I am yet to master, but you should be able to make whatever 3d object you like with it. free.

Pexels. Free stock images. And the search engine is actually pretty good at pulling up what you want.

Figurosity. Great pose references, diverse body types, lots of "how to draw" videos directly on the site, the models are 3d and you can rotate the angle, but you can't make custom poses or edit body proportions. Free, account option, paid plans available.

Line of Action. More drawing references, this one also has a focus on expressions, hands/feet, animals, landscapes. Free.

Animal Photo. You pose a 3d skull model and select an animal species, and they give you a bunch of photo references for that animal at that angle. Super handy. Free.