This is really impressive for your first game. And you did it as a team too, which is also impressive. Dividing the work makes it easier, but getting multiple people focused on the same goal adds to the challenge. Despite that you managed to create quite the adventure. All and all, I'm impressed.
There are a couple of bugs (when I die as a flea somehow the mouse is right there dead with me). And also, I noticed you could jump on ledges in the background, but there are no visual cues to indicate that. My first playthrough I thought they were just part of the background. I would recommend outlining those platforms, or adding hue or contrast or something else to make it a little more obvious you can interact with those platforms. I'd love to see this game with a little more polish and bug removals.