Adorable adorable adorable adorable ADORABLE!!!!
This is the cutest dang thing I've ever seen! The costumes are dead on, but you added your own vision! The height difference is wonderful and I'm glad you thought of it. The faces are right, but not too detailed or cluttered. The background is lovely, and I love the inclusion of Qwerty.
The expressions are a bit blah. Perhaps if Hatchy had been smiling or something it would add a bit more fun to the piece. However, it certainly doesn't detract from the work, and their faces definitely get the message across, so no harm in it.
As a sort of side note, there is a certain femininity that I always look for in drawings of Rabbit; yes, he's a boy, but he's also far more girlish than HatchWorth, The Jon, and The Spine. You captured it very nicely, especially in Rabbit's hands, legs, and face. I appreciate it.