Not bad. I particularly like how you used the Zombies 2 song to establish the sibling's relationship and character. That was really well done. 

One thing that bothered me: why exactly did Fluffy, who is so retinicent about purring, purr over so small a thing as a treat? 

As for the actual writing process, have you planned ahead what you're going to do? Myself, I need to know where I'm going to write a good story- I need the beginning, the end and a few things in between. The rest I figure out as I go along. But a lot of writers do better starting at the beginning and going on to the end without really knowing what the end's going to be. Still, if you're stuck, figuring out where your story is going, or at least what happens next, seems to me a pretty good idea. And, if you're running out of ideas for a chapter, maybe that chapter doesn't need to be as long as you thought it did.

I hope this was helpful. 

I agree with Xaopve on pretty much everything they said; the story is very interesting, but I'd make sure you know where you're going with it. Also, I might end the chapter at "Something hit me in the head and I blacked out". Then the next chapter could start with Bradley waking up with the IV needle in his arm, and you could write from there. If you're still stuck, some questions you could ask yourself are: 

Where is Bradley waking up?

Who screamed "WATCH OUT, BRADLEY!" (If it was Ariana, you might say that it was her just for clarity's sake) 

Who hit him in the head, and how did they get into his house without him noticing? Do they have some sort of stealth technology?

Why does he have an IV needle in his arm? Is he being experimented on somewhere? 

Why did the person who hit him in the head specifically target him? Are they gathering a particular selection of people for an experiment? Is this a dystopic world where he's secretly in a rebellion, and the person who hit him in the head is part of the controlling government? Okay, so that last one was pretty far-fetched. But still, sometimes randomly brainstorming can lead you to some pretty cool ideas. I hope this helps! Oh, and one more tip-- try reading it out loud to yourself or someone else. You might spot some things that don't sound quite right, or you might think of a new idea for your story!

I'm using all of those ideas!! Here goes!

~Chapter Two~

"Ohhhhhh... Where am I? Why am I even here?" I said, as I woke up. I looked at my arm, and there was an IV needle in it. "Bradley! Oh, man, I thought you were dead! That thing, whatever it was, hit you in the head so hard, you instantly concked out. I'm so glad you're ok!" Ari said, hugging me. "Back off, girl. He's dangerous. He needs to be alone, until we can figure out what kind of powers he posseses." A guard said. I instantly recognized him as Officer Ryder, my hero! "Officer Ryder, I'm not dangerous. I'm just a plain, normal, ordinary guy who just got knocked out be a Frizbee...thing. So, can I be let go?" I said. "No. You posses powers that could end the world. It only is in about 19% of the population. We're trying to extract the powers from you. Ariana, you need to get out of here NOW." Officer Ryder said, pushing Ari out of the room. "But--But--But he's my brother!! Ok, maybe we can compromise here. I will give you...Hmmm, I will give you... $55 and a cookie! I was saving it for a snack later, but you might need it. To let me see my brother!" Ari said, digging in her purse. I felt a little dizzy, so I fell alseep. I woke up a couple days later in my house in my bedroom. "Ohhhh... It's the same thing over, and over again. Ok, first thing to do: Take down those Office Ryder posters down, and throw them in the trash." I said. As soon as those words came out of my mouth, the posters suddently vanished and appeared in the trash can. "Wow. Just...wow. That's just crazy. Eh, maybe Officer Ryder was right. What else can I do?" I said, getting off my bed. I walked to the yard, and saw Ari out in the yard, dancing with some of the most popular girls in town. "Ari, what are you doing?" I asked her, walking towards them. "Dance. Off. Let's GO!!" Lizzy, the leader of the group, said. "Yeah, let's go. The song: 'The New Kid In Town!' " Ari said, her bright red hair flowing in the wind.

Well, sorry about the cliffhanger, but that's all I have written down so far. I hope you liked it!