Chifuyu & Madoka Orimura are both played by Luci Christian. It's almost certainly due to the fact that Madoka looks like a slightly younger Chifuyu. Christian also voiced Ran Gotanda in Season 1.
Charlotte Dunois (and her mother) and Clarissa Harfouch are both voiced by Shannon Emerick.
Yuko Tanimoto and Laura Bodewig are voiced by Tiffany Grant.
Tabane Shinonono and Kaoruko Mayuzumi are voiced by Allison Keith.
Allison Sumrall voices Kiyoya Aikawa, Nagi Kagami in season 2, and Riko Kishihara in season 1.
Tiffany Terrell voices Sakuya Yorutake, Shizune Takatsuki, and Riko Kishihara in season 2.
Monica Passley voices Honne Nohotoke, and Nagi Kagami in season 2.
Bad Export for You: The author had some fits with the publisher over an allegedly unauthorized Chinese localization deal, causing the series to be put on hiatus for a few months.
Creator Couple: Tiffany Grant, who was the English dub's scriptwriter in addition to voicing Laura Bodewig, was married to ADR director Matt Greenfield at the time of the series' North American release. They have since divorced.
Okiura has been I.S's illustrator for the first seven volumes. From volume 8 onwards (as well as reprints), CHOCO replaces Okiura as illustrator as part of the author switching publishing companies.
Double for the animators: Media Factory was tasked with animating the story, until Overlap took over by the second OVA and season 2.
In the English dub of Season 2, Tiffany Terrell replaced Allison Sumrall as the voice of Riko Kishihara and Allison Sumrall replaced Monica Passley as Nagi Kagami.
No Export for You: The manga adaptations have never been licensed. And after the 2nd manga announced its Series Hiatus in May 2018, the scanlation group Rapid Switch that had been fan translating it decided to disband permanently. The manga resumed publication with Volume 7 releasing on September 19, 2019. Then another scanlation group finally picked up the manga, releasing Chapter 31 in February 2020. The eighth and final volume was published on March 19, 2020.
The sixth novel was delayed until December 2010, which was a six month gap between Volumes 5 and 6. Before this, the volumes had never been more than three or four months apart.
After Volume 7 was published in April 2011, the author apparently had some kind of dispute with his publishing company. The result was that Volume 8 didn't get published until April 2013. In June 2013, Yumizuru mentioned (in an author's note in the reboot manga's 1st chapter) that he was working on Volume 9, but it still has yet to be released.
Volume 9 was finally released on April 25, 2014, exactly one year after Volume 8.
Volume 10 was released on July 25, 2015, 15 months after Volume 9. Seems like a pattern is developing...
Volume 11 was released on May 24, 2017, 22 months after the previous. The author himself even admitted in the afterword that his writing speed is a shadow of what it once was.
Volume 12 finally breaks pattern by releasing on April 24, 2018, "only" 11 months after the previous one, but the afterword announces that Volume 13 will end the series. As of 31 July 2022, it still has not been published, making this far and away the longest delay in publishing in the series history. The COVID-19 Pandemic, which disrupted practically EVERYTHING ELSE, certainly didn't help.
. The manga resumed publication with Volume 7 releasing on September 19, 2019. Then another scanlation group finally picked up the manga, releasing Chapter 31 in February 2020. The eighth and final volume was published on March 19, 2020