Manga/Anime
- Celebrity Voice Actor: Hiruma voiced by Atsushi Tamura, member of the Manzai duo London Booth No.1 No.2 along with Ryo Tamura.
- He Also Did: Yusuke Murata, the artist for the series, managed to win the Mega Man Robot Master design contest twice. He created both Dust Man from Mega Man 4 and Crystal Man from Mega Man 5. Incidentally, one of his friends created Star Man, also from '5.
- No Dub for You: The English dub for American audiences was canceled because of the deal with NFL Rush falling through, and the fact that the manga barely sells enough copies in America to avoid cancellation.
- Referenced by...:
- Good Luck Girl!: In Chapter 41, Ichiko moves past her biological father in the style of Eyeshield 21.
- One Piece: In Thriller Bark, one of Hogback's minions is a bat with the number 21.
- Heartcatch Pretty Cure! A Bridging: In Episode 6: A Cure's Chicken Soup Sena points out that Sayaka had mistakenly joined the American football club instead of the soccer club.
Other
- The NFL sponsored an anime about American football in Japan — a very successful series.
