Not bad, but you could improve a few things...
When I saw the title, I immediately thought: "Oh, cool! a flash about pokemon as real animals, this has a lot of potential!!" Sadly I was disappointed I didn't get to see Squirtle depicted as a realistic turtle or even Pikachu as a mouse, instead, the starter pokemons got replaced with...a dog, a cat and a snake? kind of sad, but I let that one go. Now to the actual review.
First, the voice/music/sfx. I don't know if it's the microphone you used or the amount of compression of the audio, but the quality of the sound was not very good, and with flashes with voice acting, you shouldn't save space by compressing audio, it should be the highest quality possible, keep that in mind for the next one. But I did like the fact that you used real music from pokemon games, thumbs up to that.
Second, the art, it's okay if that's your style for the characters, simplistic is not bad, it's actually better, because it's easier for the author to animate and easier for the watchers to remember, but come on, at least make decent backgrounds, it looked like you drew them in one minute, and most of the time there was no background at all.
Third, the humor. When I saw that proffesor Oak didn't remember Gary's name (just like in the games) I though: "Oh no, please, no, not that same joke again, please!!" and of course, you did it...I think it's the third time I see that joke, Oak not remembering his own grandson's name, Ash saying some insult, and Oak believing it is in fact his grandson's name...
Not sure how many pokemon parodies you have seen, but try not to copy jokes, even by accident. This joke was like almost a tradition, so it's okay, but just saying, be careful. For the rest of the humor, it was okay, but please, don't use memes, I'm serious, they're not funny. If they're just slight references and placed in the correct situations, they're funny, otherwise it looks like you forced them into the flash, and they just look out of place or something.
I guess that's it, I can't say much about the story, it's a parody so you don't have to think up a story, just try to follow the actual events from Pokemon, but with funny twists, and you will do fine.
I look forward to your sequel, I'm sure you will improve. But for now, you get 7/10 and 4/5