I've suggested this on Klei streams half-joking a couple times, but I do believe the following would in fact make good co-op oriented enemies. Here's a somewhat brief idea of what I had in mind:
Scissor Lizards
- Dangerous to run with/from
- Found in caves (perhaps a caves form of the dirt track following in the overworld?)
- HATE Rock Lobsters
- Attack 1: Attempts to grab a player (not in melee range) with forked tongue, if player is caught, will be put in panic state similar to getting immobilized in Ewecus snot requiring other player(s) to either manually free them by clicking on the player to untangle them (for your Wendys and Wes), or by doing a good amount of damage to the lizard in a short amount of time (intended for characters like Wolfgang who hit significantly harder). Captured players would otherwise be smacked a few times similar to the Ewecus fight before freeing themselves.
- Attack 2: Attempts to strike players in melee range with scissor like claws, has slightly more range than usual enemy melee attacks.
Paper Tigers
- Actually made of papyrus
- Hide/emerge in reeds (think the way snakes come out of viney bushes in Shipwrecked)
- HATE Scissor Lizards
- Attack 1: Lunges at players similar to the way an angered catcoon does and knocks players down (think about using the waking up animation when struck by this so that you can't simply facetank it and giving it an attack speed similar to that of tallbirds so that you'd want to dodge after getting back up)
- Attack 2: A simple swipe, maybe with a bit of cleave similar to the giants
The general concept is inspired by the Magic: The Gathering card game which also used these creatures, but naturally the Don't Starve spin could be something like this. Oh and if the joke wasn't obvious, Rock Lobsters HATE Paper Tigers.