Ask Serious Rainbow is an Ask A Pony Blog staring Serious Rainbow, a version of Rainbow Dash that adopted Scootaloo and entered a relationship with Applejack. Oh, and she's also a member of the Serious Foundation, a group dedicated to the protection of the multiverse. And she's good at it.While mostly SFW, there are mature themes and cussing is quite frequent, but nothing too NSFW (she has another blog for that). Her Scootaloo also has a blog.
This blog contains examples of the following tropes
Arbitrarily Large Bank Account: The Serious Foundation pays very well. Rainbow apparently singlehoofedly paid for the Dashpad (and presumably the repairs it requires).
When the Dashpad crossed over with A Touch of Diamonds (the Rarity crossover blog), Serious brought $400,000 in cash to cover any damages Epic Dash might cause.
Archenemy: Green Eyes, the Pinkie from Rainbow's old universe, was set up as this, but it turned out Rainbow wasn't exactly remembering it correctly.
Badass: Serious Rainbow herself. Kind of need to be in order to be a Serious Foundation agent.
Berserk Button: Threatening her family is a big one. Trying to steal her Tragic Keepsake hat is another, as is insulting old gen games she enjoys. Mentioning Gilda is another.
She isn't fond of actual cheaters either, as she and AJ are open and honest with each other. Apparently, Gilda cheated on Serious at some point and that's why she hates her so much.
Face-Heel Turn: Twilight in Serious Rainbow's original universe. Originally, she'd said it was their Pinkie (Green Eyes), but it turned out her memories were just messed up to the point she confused the two until Green Eyes pointed it out.
From the Mouths of Babes: Scootaloo's first appearance, after Serious gets asked a question about her, involves her barging in on Serious while the latter is answering that she became Scoots's legal guardian because her stepmother was a royal... something. Scoots immediately picks up the slack and unabashedly reveals that Serious was about to say "royal cunt".
Happily Adopted: Scootaloo is adopted by Serious Rainbow, and quite happy with it.
Impossibly Cool Weapon: Serious Rainbow has a Desert Eagle forged from her original universe's (Long story short, she's a reincarnation of another Rainbow Dash killed in a different universe than the one the blog takes place in) Elements of Harmony.
However, after the events of the Season 4 premiere, she forced Green Eyes to take it back to her original universe. Just in case. She did get the Manticore from Metal Gear Twilight though, so it's all good.
The Multiverse: Takes this to its logical extreme by having her be in an organization guarding the multiverse. In addition, both the universe she lives in and her original universe (long story short, her Pinkie Pie went crazy and killed the group (though apparently she was at least somewhat sympathetic and Rainbow's memories were screwed up and she mixed her and the real killer up) and she was reincarnated in another universe) have drastic differences from the show which are explicitly stated to be due to being an alternate universe (Rainbow refuses to join the Wonder Bolts, for example, due to her ridiculous wealth and personal friendship with Spitfire and in her original universe was named Rainbow Flash). Oh, and somehow, the Elements turned Discord good.
Resurrective Immortality: Apparently par for course for all Serious Foundation agents, should Serious get killed, she just respawns a few seconds later.
Retcon: Despite originally saying it was her Pinkie that killed her in her original universe, Serious Rainbow eventually reveals it was her Twilight that did it. Said Pinkie (nicknamed Green Eyes) lampshades this by saying the original story guide said she was the villain and they're not following it anymore. Also explained inuniverse in that Rainbow's memories of the event somehow confused the two and spending time with Green Eyes helped her remember what really happened.