The Guren no Hibi manga is drawn by Aoi Nanabu (Circle name BLUEMAGE), an artist known for doing hentai doujin with very shapely characters (perfect fit for Senran Kagura). An interesting note is that one of his favorite characters is Yuuka, whom Hikage resembles considerably. It's believed a contract is stopping him from doing doujins of the series.
The series' artist, Yaegashi Nan, has drawn hentai and other NSFW material before and during Senran Kagura's incarnation.
Creator's Favorite: Takaki once stated in an interview that Hibari was his favorite character in the series and designed her turnover after his love for track suits.
Dear Negative Reader: Mixed with a bit of Doing It for the Art. Takaki himself was addressed about the issue of alienating people with the series' heavy focus on fanservice during an E3 2015 interview with Technology Tell and stated that he honestly doesn't care for those who are turned off by the fanservice, as long as he gets to make the games for him and fans to enjoy.
Dueling Games: The PC port of Shinovi Versus with the PC port of Onechanbara: Z2 Chaos, both being fanservicy, Dynasty Warriors-esque action games. That said, it's more a friendly rivalry since both are made by the same company.
Executive Meddling: XSEED Games was forced to remove the 'Intimacy Mode' from the PS4 version of Burst Re:Newal after Sony apparently refused to allow the game's release with the mode included.
Tip of the iceberg, it seems; increased censorship from Sony on all of their games in both America and Japan has caused Marvelous to "seriously reconsider" how fanservice is dealt with from the seventh game onward. This didn't sit very well with series creator Kenichiro Takaki, who left the company in March 2019 leaving 7EVEN stuck in Development Hell for the time being.
Senran Kagura borrows a lot of names common to Ninja legends. But this entry is not about that. The ending theme of the anime adaptation is titled Fighting Dreamer, which is one word shy of an opening theme of a certain famous ninja anime.
The Other Darrin: in the Shinovi Master adaptation, Haruka is now voiced by Gertude Cruz instead of Teri Rodgers.
Playing Against Type: Homura's not the usual type of role for either her Japanese or English voice actresses to voice. Although a flashback in the anime showed that when she was still a good shinobi, her voice was much higher, even having Monica Rial doing her usual cute girl voice in the dub.
Screwed by the Lawyers: Initially the Ikki Tousen characters were not available in the overseas and other Asian versions of Estival Versus due to the rights issues. There existed retextured versions of the characters, but only so that overseas players can still battle against those in Japan using them and are not available for download. The characters have since (when the PC versions were released) been made available, where they become available in all platforms, albeit with a slight name change (using the original Chinese renderings of the people they were based on rather than the Japanese renderings used in that series).
The older concept art reveals that series was originally going to have flat-chested characters instead of big-breasted ones. The only character who stayed true to there original concept, and serves as a nod to it, is Mirai.
Some of the New Wave shinobi are actually scrapped concepts of the main casts:
Hisui is based on Asuka's scrapped sentai ninja concept.
Muramasa is the combination of Hibari's old robot design and Haruka's early character design.
Syuri is the early concept of a magical girl ninja, which, jarringly enough, was originally going to be Hikage.
In a similar vein, Ryobi was originally created as a potential design for Rin.
In Shinovi Versus, the Crimson Squad's ending was originally meant to be the canon ending, but due to a combination of the skyrocketing popularity of the Gessen girls (Yumi especially) and the lukewarm reception Deep Crimson received, this was ultimately changed, and the canon ending became the Gessen ending with elements from the other three endings added in.
Takaki originally drafted Portrait Of Girls to end with the Hanzo and Hebijo girls final confrontation resulting in a Mutual Kill for both sides. This was changed after he realized that the game had the potential to lead into a franchise.