This ended up longer than I thought it would be, but apparently my mind was like "hold up u forgot dis - dere u go m8" so uh, have fun reading...?
This is really well done if this is your first real short - I've tried animation myself, and it was hella hard. Great job! A few things, though - perspective was good for a few places, (ex. House) but some areas seemed to need a little work. At the beginning, the tree root was no biggie, (tree roots are really hard to work with,) and when the cat jumped to follow The Old Man, it seemed a little strange. The cat jumped straight forward when there was a small hill. From the viewers POV, the cat was somewhat behind it, seeming a little odd, but once again, it's an easy fix and no biggie. It was the same for the rug in the house - the table and fireplace had the right perspective angle, but the rug remained a rectangle. You would essentially have the same shape as a long rhombus, but everything else seems great.
The attention to the background and the scenes stayed simplistic like the characters and style, but it was still detailed just enough. I especially loved the trees - I recently took a class that included drawing a BUNCH of trees, and I'm really glad you included the little "bird holes" in the tree leaves. Well done!
The voice acting was good if you've never done it before, but seeing as this character is "The Old Man," I would've had a bit of a more scratchy, old sounding tone to it. Some parts of the dialogue could've been carried out better but people (including me,) tend to get slowly get quieter when they perform. It could've also been the microphones issue, but don't be too worried about that - as long as the audience can tell what in the dickens you're trying to say, then it should be fine. The music was carried out much stronger than the voices in some places, though, but it's not surprising seeing as those were used from more pure audio files, if that makes sense - raw recordings tend to be a lesser quality than those with professional equipment. I suggest for the future that when you talk after music has started playing, just put the music in the background; tone it down a bit, so you still have the music in the atmosphere while still getting your point across.
Oh, and another thing - anatomy? PEEERFECT! The walk cycle on the cat was done just right, and it's one of the hardest things for me and many other people alike. The Old Man's anatomy was done great as well, and I like the fact that you actually included visible joints and really showed that this man does indeed have a skeleton. (I thought the stomach was amusing, too.)
All in all though, it's been done beautifully, and I love the plot. You stuck with an idea and didn't get carried away - simple but enjoyable. I'm sure your friend is gonna really like this, though! :D
This would also be a cool thing to reanimate once your animation skills grow and improve.
(But that's just me dON'T FEEL OBLIGATED TO DO SO IN THE FUTURE-)
Apologies for the lengthy review though, for some reason this really spoke to me. Some of this is probably just me being snarky and picky, but then again, I'm also just an artist who is weird about some things..! Anyways, keep up the good work man!