I'm guessing this must be your first animation. I'm not going to lie, it wasn't really too good in my eyes, let me explain.
Though the signing to make music was somewhat cute, I think it would have been better if you used music samples from either the Pokémon games, or some samples of royalty free music. Background music usually helps add fullness to a scene that would otherwise seem a bit empty without it.I would suggest snooping around the Audio Portal for some tracks to use for your animation. Make sure they are marked as royalty free or free to use in web animations though. If you are unsure if a track is
I'm not going to complain about your art style, since it seems like you are just starting out with it, although, I will say that your scenes feel pretty empty on a visual level. There is clearly a foreground, but the background is non-existent You should try adding backgrounds to your scenes, such as a sun, or some trees when outside; maybe some computers, desks, and science related stuff when they are in the lab. Scene design is quite important when making animations, as it helps make the area the characters are in more convincing. If you need inspiration or ideas on how to make good backgrounds, try watching some cartoons or animations and pause it every now and then, taking note of what is going on in the background, why it's there, and how everything is placed.
I agree with doggenhausen that your microphone quality is really good, and your voice acting is pretty alright; however, it does all sound like it was recorded in one take in one audio file. Try recording each line as a separate audio file, as this can help reduce awkward pauses of silence in the animation as you ready up what you are going to say next. It's also good practice in general, as it's easier to modify and edit short singular audio files than it is to edit one giant audio file.
Keep these things in mind when you start making the next part of your animation, and I'm pretty sure it'll come out better than this one.