[PHB p177]Quote: An awakened tree or animal can speak one language that you know, plus one additional language that you know per point of Intelligence bonus (if any).
Me: The somatic can be adapted to the animal's physiognomy. Hops and skips for a mouse Wizard instead of the finger wiggles used by a human. So an animal spell caster is possible.
Which leads to this idea. How about an awakened animal campaign? A bear Paladin, wolverine Barbarian, hawk Cleric, and fox Rogue off to explore the world, and stop the Big Bad. They look like their unawakened counterparts, act like their unawakened counterparts, but they can talk.
A hawk that can raise the dead.
Think of the possibilities.