The Danza: Venus is based off of Bemani musicians DJ YOSHITAKA and Sota Fujimori, who use the alias "Venus" when collaborating together for songs.
Invisible Advertising: peace was released with virtually no promotion or location-testing other than an announcement the day before it. This is a little suspicious, given that SOUND VOLTEX Vivid Wave was announced around roughly the same time with the usual pre-release promotional routine.
Keep Circulating the Tapes: The "POWER FOLK" songs were removed from the series after the composer, Atsushi Shindo, was accused of plagiarism. They can still be found on YouTube, however.
Licensed Game: Along with the regular games, there were also pop'n music spinoffs with songs from specific licenses. This includes Mickey Tunes, or Disney Tunes as it was called on the PlayStation, which has Disney songs with Mickey Mouse and friends as characters, and the Animelo games, which have songs from various anime.
Missing Episode: The full version of "Airport Shuttle" has been removed from Nico Nico Douga, and can't be found anywhere else.
No Export for You: Only the first arcade pop'n music, an XBLA adaptation with a small number of songs and a low difficulty ceiling, and an In Name Only Wii version have been released outside Japan. While Round 1 locations in the US do carry pop'n cabinets, they are all running old offline versions rather than current, online-required versions. Even non-Japan non-Korea Asia doesn't have access to current pop'n versions!
Real Song Theme Tune: Cover versions of J-Pop and Anime music that litter the game (and even international hits in Partynote The game has two songs from German Europop group Dschinghis Khan. Also, the Disney version and Animelo versions of the game.
The reason why the full version of "Airport Shuttle" is now a Missing Episode is because Konami owns the rights to the song, and are thus the only ones allowed to release it at all (or not).
What Could Have Been: NEW Pop'n Music: Welcome to Wonderland! had a location test at JAEPO in early 2020 with various drastic gameplay alterations, including the usage of an NFC figure system and slide notes, getting a very negative reception from fans. Ultimately, a full release never materialized and a more traditional installment in the form of Kaimei Riddles was released later that year instead.
General trivia
Mashing buttons at the ends of some songs triggers some special sound effects:
Chibikko Idol / "Otome Rumba": "Hanya!"
Gradius / "Gradius -Full Speed-": Sound effects from the arcade version of Gradius.
Hokuto / "Ai Wo Torimodose!": "ATATATATATATA!" "WA-TAH!"
Older versions would only allow you to play EX charts on extra stages. This was later relaxed so that only new songs have locked EX charts, and even then only require playing the Hyper to unlock the EX.
. It's not available in the PS2 versions, due to the Mario franchise being owned by a rival console manufacturer.