Beautiful graphics and audio.
The mechanic is really well implemented, with each dog having a personality. Really nice!
The only thing that could be improved in my opinion is a way to notify the player on what he can actually do. I had a hard time finding that I could jump on top of Roy with Darwin, even though I tried the first time, I think I didn't insist enough and thought I couldn't. At the end I managed to do it :), and arrived to the exit :).
It should be made clear where the player can jump and where he can go I think.
Really great job nonetheless!