You did quite well on this picture, but for one thing you could probably improve on, is that you should probably use your pencil lighter, so that you can erase more easily, so we won't see all of the eraser marks.
The FFFF guy was quite a nice touch though.
Another thing you may want to work on is Maria and Alex's impression, and you may want to fix Alex's tail, and Alex's hair may want to be fixed as well.
Alex's arms look to skinny as well.
Well, I hope this critique helped. You did a very nice job thought.