To everypony reading this not familiar with the "Sonic the Hedgehog"-franchise, "Cosmo" (left) is a character from the cartoon "Sonic X", season 3. She is the sole survivor of an all but extinct race of sentient plants. Apparently turning into a tree is commonplace in her culture.
Eh. Figured that while the caption adds a bit of a joke on one side, it also takes something away from the lightheated-ness of the image. So … here's the same image, except with no caption.
Same picture, except with a (somewhat) black-humor'd "My little Pony" / "Sonic X" in-joke caption, not exactly in the spirit of the image itself can be found here: [link] (caption has been slightly updated, too)