so the extras folder is just a bunch of indev stuff i've made over the span of the model pack that never actually got
released. everything listed here is either not completed or has MAJOR issues, which is why it's not a part of the main 
pack, so use at your own risk!

here's notes on what's wrong with everything:

-knuckles was never completed, and only has a few animations.
-super sonic for icezer's super sonic mod was made before i made a lot of texture and blend changes to the sonic model,
so it won't be exactly up to date with those changes. i haven't used it in a while but as far as i remember it's still functional? there might be some animations exclusive
to the mod that i didn't do though, i don't remember
-sms doesn't have a model for smso, hms, and hmso, so if you're really itching to have a crispymodels sms, unfortunately 
you'll have to use someone else's sms model for those
-rosy is amy's cameo model, i completed all of the animations but unfortunately she's not in the right place for most of
them. only use if you REALLY want a crispymodels amy cameo model, but beware the major problems with it!
-the tree IS fully modeled, but it has 2 other variations that i didn't complete, so it's just the regular variant.
therefore, if you use this model and you're in a map that has one of these other tree variants, it'll just show up as the
regular tree.
-the tails in the extras folder is the original one from the initial release, it was never completed before i started over
with him but he's there if you want to marvel at how bad he looks

and finally, here's the models.dat lines for the extras

KNUCKLES CRISPYMODELS/EXTRAS/KNUX.md3 2.7 0.0
SUPERSONIC CRISPYMODELS/EXTRAS/SSONIC.md3 2.5 0.0
SMS CRISPYMODELS/EXTRAS/SMS.md3 2.5 0.0
ROSY CRISPYMODELS/OBJE/ROSY.md3 2.4 0.0
TRE1 CRISPYMODELS/OBJE/TRE1.md3 2.5 0.0
TAILS CRISPYMODELS/EXTRAS/TAILS.md3 2.5 0.0