I can't find any info about them on the wiki (other than functions used to read from them) and none of the editors I've used actually allow them to be created. I don't even know the file extension for them. Is there any info at all on these things and how to go about creating them?

The standard Sphere animation format is MNG.  It's a variant of PNG that supports animation.  Both legacy Sphere and minisphere support it.  Sphere 1.x also supports .FLIC (or something?) but I don't think there's any software still in existence that can still write that format.

It might be difficult to find software that can write MNG files too, it's basically a dead format at this point.  Once the patents expired on GIF, MNG just kind of died off.

I think the easiest way to make an mng would be to make a gif or apng, and then use ffmpeg to convert to mng.

And to be fair, back when Sphere was young, mng was a serious contender to gif. It's still superior in many ways, but now apng has surpassed it...for some reason.

Huh, that's interesting. Never knew about that format... Might even be worth trying to make some just to see how it works. Might actually use them in my project for the hell of it. Thanks for the info, guys.

UPDATE:
Well, obviously, it turns out you all were right, could barely find anything that even knows what the format is. GIMP, I found out, is able to export files as .mng (but can't open them?!) So yeah. Dead format.

The file I exported from was read by Sphere (1.5) and the functions seemed to work, except for getNumFrames(), it always returned 0. Well, either way, it was an interesting little history time travel thing. Obviously not a format worth the effort making anything with.

Yea, I did tests with MNG in Sphere around 2004 or 2005 or so and found it much easier to simply create a spriteset and animate it in code or using map engine command queuing.

Most likely I will drop support for .mng in minisphere 4.0 and lose the dependency on libmng.  It's kind of just a curiosity at this point.  I think the only major Sphere game that actually uses the Animation API is Kefka's Revenge and that game has other issues preventing it from fully working in minisphere, so given the lack of software support for .mng its probably best just to drop it.

As NEO says, you can always get the same effect with an animated spriteset.

By the way, @Datomas, I fully recommend upgrading to minisphere.  Sphere 1.x is no longer maintained and minisphere has a ton of new features (and is much faster!).

Yeah, I'm looking at minisphere now at the moment, but it introduces a lot of concepts I can't seem to wrap my head around just yet. Like CommonJS modules, don't fully get how they work... I've got a lot of brushing up to do, but I did look at the Sphere 2.0 API and I'm pretty psyched about the features.