Executive Meddling: Liveman was originally supposed to be a three-member team through to the end, until the producers realized it was the tenth Super Sentai show since the franchise's revival with Battle Fever J and they wanted to do something special. Thus, Black Bison and Green Sai were added to the team mid-series. This caused some plot holes with previous episodes (such as the fact that Yusuke was unaware of Tetsuya's existence, despite being acquainted with Takuji's other brother Takeshi in an earlier episode), but also led directly to the introduction of the Live Boxer and Super Live Robo. A net positive, all in all.
Anyone in France ever watch "Bioman" way back when? Then you'll recognize Prof. Dorothy...
Episode 27 features a guest role by Junshi Shimada (Prof. Yumeno) as Yoichiro Misaki, Megumi's father.
Also Yoshinori Okamoto AKA Dr. Ashura was another Toku villain, namely Space Pirate Booba (only way you'd recognize him is from his battle cries, since Booba covers his face with mask all the time), as well as a short-lived villain in Choushinsei Flashman, Bo Gardan.
Also Takumi Hirose as Dr. Kemp, bringing forth three Flashman alumnus together in a reunion.
Dr. Hoshi is Daisuke Ban of Kikaider fame, although he is better known to Sentai fans as Makoto Jin (the second Battle Cossack).
What Could Have Been: There was a planned Filipino adaption of the show (despite the series haven't aired in The Philippines) said by famous cosplayer Alodia Gosengfiao, saying she'll be going to Academia Island. Pinoy Sentai fans rejoiced that they'll get to see a Sentai again (even though it's an adaption), only for her to say days later that it's a false joke on everyone to promote the Animax Asia airing of Haruhi Suzumiya. You just had to ruin the excitement, Alodia!
An In-Universe example comes with the prototype suits which were supposed to be used for space exploration seen in the very first episode, Takuji Yano and Mari Aikawa's suits are a swallow and a dog. That would be a Wild Mass Guessing.