Ok, Blitz, I watched all five of your videos, and I just took a few notes while I was watching.
First of all, you quick attack too much without cancelling it. In fact, I don't think I ever saw you cancel it. Doing this left you open for punishment again and again. You need to cancel it next time by jumping as soon as you hit the ground. You can use aerials, tjolts, thunder, etc out of QACing.
I think this has been said, but I'll just reemphasize it: you should not stand still as much as you did. If you are trying to think of an approach, then back off and pressure your opponent with tjolts while your thinking. Also, with your tjolt usage, you mostly used them well. I did note however that you would sometimes use tjolts when your opponent was right below you. This is a no-no because they can get easily take advantage of your vulnerability and hit you.
In one of the first videos, you used skull bash offensively a ton. I wouldn't recommend this because it's trajectory is predictable, and it's easy to avoid/punish.
Now for thunder usage. You were a little careless when using thunder at times, and like everything else I've addressed, it left you wide open for punishment. Thunder is a great move, but if you're hitting an opponent on the ground or close to the ground, you have to be more aware of the platforms above you. A few times, I watched you thunder to hit your opponent, and the platform saved them. Not only were they saved, but they smashed you across the stage.
Ok, my last bit of criticism before I go to praise. When you were playing Ike, you got waaay too agressive. You would quick attack into him and not cancel it (not that you should qac much against Ike either). You would be the one to approach him most of the time, and he took advantage of that. You would roll around him to find a good angle, and he would just charge a forward smash and wait for you to roll into it. Once you let him take the offensive, you began to play a lot better. Remember, Brawl is a defensive game. You should have pressured the Ike with more tjolts and baited him into attacking you.
Now, there were some things I liked about your pika. My favorite thing was that you actually utilized bair. True, sometimes you would do it too close to the ground and have landing lag, but you effectively used it to get people off of platforms, which is what you are supposed to do. Another excellent part of your game was your short hop dair usage. Your opponent never seemed to expect it, and it worked well. Last thing I'll say, good job using Pikachu's sexy chaingrab. You really took advantage of the fact the other player didn't expect you to pummel so much and didn't even try to get out of the grab. Bravo.