This design has an easily accessible zip but it’s not trying to pretend to be the mouth – it sits just behind a flap with a decorative little plushie-kitty face on.
(Okay, I spent an afternoon reinventing the pyjama case.)
ETA: Tibsy Cat – Smaller
Same idea on the bear shapes (adjusted to make the smaller doll much slimmer)
… and zip-mouth dogs based on the knitted dog photo
These would sew up much like my tall worry monster pattern in fabric, or they could be done in felt/plushie without needing to turn/topstitch. Ears done the way I do the ribbon ‘hair sometimes’, flopping forward over the face from the top seam. Could be really tactile with a silky fabric on the inside of the ear and plush on the outside. Tail wouldn’t be difficult. I don’t think the zip-mouth makes these look un-dog-like (unlike the cat and the bear, who’d need a shorter and less obtrusive zip if done this way). I’m not sure it’s possible to get the lovely floppy tongue from the knitted dog in there. A felt flap sewn on just below the zip track, maybe?
Okay, stopping now. Monsters won’t sew themselves!