Steven Moffat/WMG

Steven Moffat is from the Monsters Inc. 'verse.
This is why his Doctor Who episodes are all both soul-destroyingly terrifying and full of some of the funniest lines in the series: he's harvesting both laughter and screams.
 * In that case, he's wearing a disguise. I bet he looks like a horrifying Eldritch Abomination who pulsates terror.

Steven Moffat is planning to slowly replace The Doctor with River Song
He has a five-year plan in which we will start to see more of River and less of The Doctor. Pretty soon the show will be all River Song, and they'll rename it 'River Who?'. When will it start? It already has!
 * He's already  And let's not forget that River   MOFFAT MUST BE STOPPED!

Steven Moffat used River Song to extend the Doctor's lifespan.
When River saved The Doctor's life in "Let's Kill Hitler," Amy said it used up her remaining regenerations. River only seemed to use about three (Girl in New York -> Mels -> River), so that leaves 9 or 10 more that she gave to the Doctor. That could extend the Doctor's lifespan past the 13 regenerations rule, thereby extending the show through 10 or 11 more actors. Considering River is quickly becoming Moffat's pet character, it wouldn't be surprising for him to have her do something major like that.

Steven Moffat Feeds on fear
Self explanatory really.
 * So, he's Parallax?

Moffat is Parallax.
It's why he feeds on fear. Thankfully, he's a benevolent version of Parallax. Of course, Moff still needs the potent fear of children. Without it, he will get hungry. No doubt leading to the universe becoming one big den of Nightmare Fuel.

Steven Moffat is a troper.
It has to be!

Steven Moffat doesn't just feed on fear
He also feeds on confusion. He made Timey Wimey ball for a reason: fear is his breakfast. confusion is his dinner time.

Steven Moffat hates America
Jekyll has many TakeThats towards America for no apparent reason. And the episodes of Sherlock that he wrote either make Americans out to be very stupid (the one in the cab from A Study in Pink) or have them be very inept and idiotic decoy antagonists such as the ones in A Scandal in Belgravia.
 * To be fair in A Study in Pink, the guy in the cab wasn't stupid so much as weirded out by the two guys stopping his cab for no apparent reason. Jekyll and Belgravia on the other hand...
 * So?
 * On, the other hand, his depictions of Americans in "The Impossible Astronaut" / "Day of the Moon," are actually a little better and step back from the depiction during the RTD-era. Whereas the Americans under Davies time as producer were obnoxious like Henry Van Statten or annoying like Luke Rattigan. However, the Moffat-era Americans were a little gun-happy, but otherwise more even-handed (he even gave Nixon a positive portrayal.) I think it's just that America is a big enough world power right now that it's easy to pick on and makes for a quick villain. [P.S., he and his teams (Matt, Karen, Benedict, etc.) have had a lot more involvement in trying to make the show more popular in America, so there's that, although if he actually does, I can't really blame him after the American Coupling.]