There were so many flaws with this.
Because I'm a Pokenerd, I become unable to sleep when someone gets things related to Pokemon wrong.
1. Absolutely NO Electric attacks affect Ground types, and Onyx is a Rock/Ground.
2. I'm pretty sure the beam Onix shot out of it's mouth was Hyper Beam, which Onix is unable to learn by any means.
3. Lets say that Onix can learn Hyper Beam. A blast like that would have knocked out Pikachu instantly, or at least badly damaged it.
If you want to make a Pokemon flash, you'd better do some research first. If you give a Pokemon an attack, make sure it can learn it. Keep in mind the type advanteges that would make an attack useless.
Ex. Ghost is immune to Normal type moves, like Tackle.
Ground is, of course, immune to Electric type moves, like Thunder, and, *ahem* Volt Tackle.
Steel is immune to Poison type moves, like Poison Sting.
Then take into account type resistances, like;
Psychic is resistant to Fighting and other Psychic types.
Steel is resistant to just about everything, but is weak to Fighting, Ground, and Fire.
The ending was just dumb. I didn't laugh at all. As for the sound, you just used stock sound effects, like giving Onix Godzilla's roar, and giving Pikachu lame footstep sounds. Also, like I said, no music near the end. The overall animation was choppy, and the lag didn't help either.