Midori no Makibao x Uma Musume (ONA promo)

The opening sequence is a faithful recreation of the one from Midori no Makibao, with the background horses and most of the human characters replaced with Uma Musume characters. The opening theme "Hashire xxo" is a mashup of the Uma Musume Pretty Derby single "Hashire Uma Musume" and Midori no Makibao's "Hashire Makibao"; both of which are covers of the 1970 Salty Sugar single "Hashire Kotaro". The title also references all of the featured characters having names ending in "O"; thus each character sings out their name in place of "xxo" in the chorus.

In the promotional materials, Midori Makibao and the Uma Musume form the letter "O" with their hands or limbs, except Calstone Light O, who forms the katakana "オ" ("O") with her body.

"Tottemo Umamimi" is a reworked version of the Midori no Makibao ending theme "Tottemo Umanami".

When Sakura Chitose O, Sakura Bakushin O, and Sakura Chiyono O do their Victory Operation pose to turn Midori Makibao into an Uma Musume, Makibao suddenly glows and ribbons form from his head. This is a reference to Tamamo Cross, as both Makibao and the uma musume character are based on the real Tamamo Cross (1984-2003).

Sakura Bakushin O, Sakura Chiyono O, and Sakura Chitose O are based on racehorses owned by Sakura Commerce, which owns the S-PARK-le pachinko hall chain and the E-Kitchen bento shop chain. As such, their racing costumes use the company's pink and white colors. Sakura Bakushin O (1989-2011) won 11 out of 21 races from 1992 to 1994 and is hailed as one of the greatest short-distance racehorses in history. Sakura Chiyono O (1985-2012) won five out of 10 races from 1987 to 1989, including the 1988 Tokyo Yushun (Japanese Derby). Sakura Chitose O (1990-2014) won nine out of 21 races from 1992 to 1995, including the 1995 Tenno Sho (Autumn).

The real Calstone Light O (1998-2024) won nine out of 36 races from 2000 to 2005, with the 2004 Sprinters Stakes being his sole G1 win.

While both Sakura Bakushin O and Sakura Chitose O have sakura-patterned eyes, Sakura Chiyono O has blue eyes as a reference to her connection with Maruzensky. The real racehorse was a direct descendant of Maruzensky (1974-1997).

The "O" (オー) in Midori Makibao, Tokai Teio, T. M. Opera O, Sakura Bakushin O, Sakura Chiyono O, and Sakura Chitose O means "king" or "monarch" (王), while the "O" in Calstone Light O is just an "O" (オ).