A/N: I put a lot of work into this. Sorry if it's long.

Today was officially the worst day of my life. My sister fell on the attic floor trying to do a backflip. She said her head felt like it was split into a thousand pieces. Then I had to get Wendy to call 911, and also I had to tell Stan what happened. Eventually, Mabel was being carried onto a stretcher. I helped push her into the ambulance. I wanted to get in the ambulance with her, but one of the men there said I couldn't. Come on, I couldn't see my sister when she needed me most? I couldn't stop crying. I had to wipe my eyes on Wendy's shirt sleeve.
Eventually, we got to the hospital. A nurse told us that they had to do brain scans later that evening, and we could visit her before they did. I went to see Mabel at once. "Mabel, I told you not to do backflips on the attic floor. I never meant to have you end up like this." I told her, crying on every word I said. Mabel looked confused. "Who's Mabel, why'd she do a backflip, and who are you?" she said, only putting me in depression. "You're Mabel. And I'm your twin brother, Dipper." I cried. This had to be a trick. She looked even more confused. "No, I'm an only child. And who in the heck names their kid Dipper?" she told me, raising an eyebrow. I showed her my birthmark, and reminded her how she called me Little Dipper (Even though I'm only a millimeter shorter, Mabel loves bragging about it and the fact that she's 5 minutes older than me). She still didn't recognize me. I even tried singing the My Little Pony: Friendship is Magic theme song to her. It's her favorite show. (It was worth the risk. I hate MLP.) Mabel didn't remember me, or the show, so she was hurt really badly. Because if there's anything in the world she loves most, it's me. We were there for each other all the time. Like when the gnomes tried marrying her, I warned her in advance. And when I had a job at the pool with Wendy, I risked the job just so she could get Mermando home. (She even got her first kiss that day.) Also when she got braces. She thought everyone would think the braces looked dorky, but I told her that she looked even better with braces. So, this was horrible. Those doctors needed to do something at once.
"Please, Mabel, don't forget me! You're my best friend in the world, more importantly, my twin sister. I hate to see you in this state. No matter how crazy you think I am right now, don't forget all the memories we shared! You supported me when no one else agreed with me, even if you didn't agree yourself! You are the only true friend I've ever had, and I will be yours till the end. We never turn on each other's backs in an argument, we make it up with an awkward sibling hug. If I had the choice, I'd risk everything just to keep you by my side. You can be a pain sometimes, but that's normal for people with brothers and sisters. But now I'm just an insane stranger. In reality, I'm worth anything to you. Please, just remember me. Mabel, you are the reason I never give up on anything. You always encourage me to do the right thing. You light up any room you walk in, by showing everyone your beautiful smile. Mabel Pines, you are the best sister anyone could ever ask for." I said to her, crying more now than ever. There's no way I could live without her, and all that mattered was that she remembered me soon. Of course, she looked confused, and said, "Aw. You're pretty nice for a stranger!" I let my hand reach hers, because I wasn't going to ever let Mabel go. (Metaphorically)
At 9:00, Mabel was able (Ohmigosh, that rhymes) to come home safe, with her memory back. "Dipper, what you said in the hospital was sweet. I feel the same way. We shall always be twins and best friends. From the womb to the tomb." she told me. "Awkward sibling hug?" I asked her. She didn't dare turn down the chance. "Awkward sibling hug." So we awkward sibling hugged, and remembered to always trust each other. That's what twins are for.