Anime First: The anime came out before its companion manga Umayon. Inverted with the Haru Urara and Starting Gate! comics, which came out before the game or anime did.
B-Team Sequel: Season 2 Studio Hops from P. A. Works to Studio KAI (of Cagaster: Of An Insect Cage), though P.A. is still credited as an animation co-producer and handles a few of the episodes themselves.
Following Episode 7, Netkeiba, a Japanese website devoted to Horse Racing, reported that their page about Silence Suzuka (the horse, born 1994, died 1998) has risen to number 1 in hits.
Expanding on the earlier point, the anime ended up promoting Japanese horse racing or just horse racing in general more instead of the mobile game as intended on the international stage, if the huge amount of Reality vs Anime comparison videos of the races surfacing on the internet is anything to go by. Not to mention judging by the more recent comments, Youtube videos of the featured races became dominated by viewers who admitted to having this anime act their gateway to the world of horse racing especially in the 1998Tenno Sho. And that's not counting the huge amount of examples in the shout outs page that casual fans never knew about until the anime aired...
Harpo Does Something Funny: The voice actress for Gold Ship mentioned that she has to adlib at lot of Gold Ship's background chattering. For instance, in Episode 8, when they went to make wishes during hatsumode (the Japanese New Year ceremony), the final part Gold Ship's wish was not specified in the script. (It ended up being a nice tirade starting with "that orange juice starts coming out of faucets"). Seeing as Gold Ship is quite spontaneous and goofy, this sounds like a mild form of Enforced Method Acting.
I Knew It!: Anyone that is savvy with history of the horses will know what is going to happen to their corresponding horsegirl counterparts along with their win/loss record. For example, those who knew about the actual Silence Suzuka guessed that its anime counterpart would suffer a leg injury. It happened in episode 7.
Yutaka Take, the legendary jockey who rode Special Week and many other prototype horses to their best victories, appearsAs Himself as a real-time commentator at Nippon Derby in Episode 5, also voicing himself, also credited. His facial expressions show him rooting for Special Week; in the corresponding real-life race he was riding Special Week. There's an extremely oblique reference to his birthday, March 15, in Season 2 Episode 3: the real race depicted in that scene, in which he was riding McQueen, took place on March 15th 1992. For no other apparent reason, Special Week therefore has a slice of cake on her head. In the rain.
The regular second commentator/analyst during the anime races is Junko Hosoe, a past jockey who is now a real life racing analyst (so her role is similar to Newscaster Cameo). She has a page on the Japanese Wikipedia. She is voicing herself and is duly credited.
The old man standing next to Gold Ship in Episode 3 of the second season is Takatoshi Imanami, who was Gold Ship's groom.
Recursive Adaptation: The anime got a chibi spinoff 4-koma manga adaptation called Umayon, with said spinoff manga later getting it's own anime adaptation.
Rule 34 Creator Reactions: The anime's producers issued a request to fans not to produce pornographic material featuring the horse girls, out of concern that it would adversely affect the reputations of the owners of the characters' Real Life horse counterparts. The problem is that this is coming from people who produced an anime where the horses are all teenage horse girl idols and the announcement would have no doubt invoked the Streisand Effect in the international anime community if the general response to it was anything to go by, meaning that it backfired big time. That said, it would appeal that for the most part people listened, as there are very few to Doujinshi featuring the horse girls at all, at least anywhere where they can be publicly observed.
Word of God: According to an April 2018 livestream from the anime's producer:
Tracen isn't the only academy out there, and the Twinkle Series isn't the only worthwhile competition; some horse girls go to other schools away from Tokyo and participate in other competitions.
The horse girls' fathers are completely normal. They also are never appearing on-screen.
Horse girls are sort of the Pretty Derby equivalent to elves.
For The Game
Cash Cow Franchise: While already fairly popular before the games debut, it very quickly became this for Cygames following the game launch as it earned over 200 billion yen in 2 months and maintained its position at the first place in the App Store rankings, only falling from the top spot once. As of current it has unseated previous top Cygames earners Granblue Fantasy, Idolmaster Cinderella Girls Starlight Stage and Princess Connect: Redive, as well as non-Cygames produced gacha games such as the long-reigning Fate/Grand Order and Twisted Wonderland.
Dueling Works: With other top-earning gacha games such as Fate/Grand Order, Genshin Impact, Twisted Wonderland and et cetera. Its also this with its brother and sister series from Cygames, but primarily Granblue Fantasy and Princess Connect.
Cygames's stance on the matter is essentially a very polite "please don't", since the game's basically a very loose interpretation of real horses in Japan's very lucrative horse racing industry, with permission from the horses' owners. Given that horse racing is one of only a handful of legalized gambling methods in Japan (the most lucrative one, to boot), in large part possible due to organized crime, the reaction is justified.
Mr. Nishiyama, the owner of the real Seiunsky and Nishinoflower was surprisingly okay with R18 art of the two, going with the justification that it helps bring some interest to the horse racing industry. After Twitter trolls made incessant Slut-Shaming comments (to the point where it was #1 trending regionally in Japan on Twitter for a time), he reversed his opinion on the matter, and Cygames insisted he just ban all fanart of the two characters. He then reversed his opinion again when the trolls stopped harassing him and the controversy died down.
Takatoshi Imanami is active on Twitter. According to his tweets, he apparently tried out the game for at least a couple of hours, and tweeted that the in-game Gold Ship was "harder to handle than the real one".