Like Fire by @darthchocolate
I freaking love the Weasley twins, and I know a lot of writers on this site have written their back stories, but this... THIS.
One thing I love about this is that you didn't add in some new OC girl that gets caught up in the Fred/George love triangle. In fact, that's what I love about all of your books. You write about the Hogwarts days of the Death Eaters and the Marauders and now Fred and George, and you always do a stunning job because you don't thrown in another random OC. You're writing their story without throwing in extra and doing a very beautiful job at that.
Don't get me wrong here; I love Fred and George Weasley stories with OCs and love stories, but I also love this where there is none of the underlying love story. It's just Fred and George. Just the way it should be.
Your writing is amazing! There are very minimal grammar errors that I've found (just the occasional forgotten comma), and I'm not really gonna nitpick on that. Honestly, the quality of the story trumps the little errors.
Your descriptions are amazing. The picture you paint with your words is a beautiful, vivid one. I love reading your story and knowing exactly what is going on and where. It's truly magnificent.
On red flag though... the ride on the Hogwarts express took like, ten minutes. I do recall that it takes quite a while to get from the King's Cross to Hogwarts. It's quite the distance.
But other than that, everything is awesome! The pranks on Filch, the concern of Percy, the twins' interest in nothing but causing mischief... it's all amazing. It's stories like yours that make me feel like I'm back at Hogwarts with HP & Co., so I'd like to thank you for taking me back to Hogwarts.
To recap, change nothing. Your story is amazing, and I highly suggest that everyone who has read this review should check it out.