lol...
Grouse can also mean like "pout" (especially over there in jolly ol' England, according to book 2 of "The Chronicles of Narnia"...anyway...), so we could also have a movie about a big bear with a big pout:
"Bear and The Big Mean Grouse"
(unless we wanna make it about a big guinea-bird with a nasty attitude, which actually sounds more entertaining now...)
Peter: "Oh Susan do stop grousing."