Shade
Monster Junkie
I doubt the Disguise check will be very good. It's a plant pretending to be an animal, after all, and it still looks like a bush.
Indeed! It's almost comical to imagine it smug and self-satisfied with its "disguise".

We might borrow and modify the imperfect change shape from the lesser ghul...
Diminished Change Shape (Su): A lesser ghul can assume the form of any Small, Medium, or Large humanoid, giant, or genie. This works exactly as the change shape special ability, except that the ghul cannot transform the appearance of its feet. The ghul therefore only gains a bonus of +6 to Disguise checks when using this ability to disguise itself.