"The Girls' Team" for the trio of Blue Rose, Dragon Kid, and Fire Emblem.
"Palmface" for Lunatic thanks to the design of his mask and Kotetsu's in-series joke. Unfortunately it turns out to not be as funny a nickname as it initially started out as.
"Moe Oyaji" for Kotetsu, in reference to his AdorkableOne of the Kids tendencies (as well as constantly being called "Oji-san" in canon).
"The catbeard" for Kotetsu's beard, which is shaped like a cat's head.
And the "crapsuit" for Kotetsu's first outfit (which is actually called a crappy suit in the second episode, and literally a "crap-suit" in the English dubbed version of the same scene).
Fandom Nod: Each On the Next segment starts with either Kotetsu or Barnaby disclosing an entirely random fact about themselves ("Hi! I'm Kotetsu, the member of Tiger & Bunny who ends up falling for idols he sees in his dreams! / "Hi! This is Barnaby, the member of Tiger & Bunny who owns five pairs of the same glasses!).
I Knew It: Early on, many fans hypothesized that Kaede would turn out to be a NEXT. Episode 17 proved them right.
Another very popular theory that turned out to be chillingly accurate come Episode 19 was that Maverick was behind Barnaby's parents' deaths, and that he was the show's Big Bad.
Jossed: A popular theory about Barnaby being a robot was proven false. But this idea wasn't entirely a case of The Epileptic Trees, since androids were later introduced as something Maverick planned on using to replace Superheroes.
Mid-Development Genre Shift: Of the first variety. Originally, the series was supposed to be much darker and more morbid in its theme and mood, with heavy drama and tragedy and different personalities for both main characters. The creators later decided to go for a more lighthearted story with an overall comedic theme accompanied by some drama; traces of the aforementioned serious tone can be seen in the second cour.
Dave Wittenberg voices Doctor Saito. He also voices a familiar Section 9 agent of the same name.
Ben Jackson was also the name of one of The Doctor's companions in Doctor Who.
No Export for You: The video game-based versions of the show are not exported outside of Asia.
Playing Against Type: Most of Masakazu Morita's fans were surprised by the fact that he could go from being the seiyuu for Hot-Blooded shounen characters to voicing a character like Barnaby. Morita himself has expressed surprise that he was cast for the role, and says he sometimes felt that he might not be able to pull it off.
While her main role in the show, Agnes, is more the kind of character she's known for, Tara Platt also plays Samantha, a kindly old woman who was a nanny to Barnaby, who is voiced by her husband.
The Red Stapler: In Japan, products even tangentially related to the series are selling out — such as a brand of wine called Brooks that uses an Ouroboros on its label and a brand of cologne with a similarly shaped bottle to one Kotetsu owns.
Throw It In: When the producers told scriptwriter Masafumi Nishida that he could write the characters any way he wanted, he jokingly asked if one of them could be a photobombing weeaboo. The answer was yes.
The show was originally going to be called 'Busty and Bunny' (presumably, 'bust' meaning 'destroy'). Of course, then the female producer did some research and found out that they couldn't call him 'Busty', because of the English meaning. Another proposed title was 'Seekers'.