If new Boys get introduced...
While the Sequel Hook of the anime showed Subaru and Naoki and hinted that they'd be added if the anime got a second season, what if they weren't the only ones?- Gudetama: Since they're a popular mascot, a Gudetama boy would be an easy choice. The anime hinted that Macchi, who already had a character arc of not wanting to accept being Demoted to Extra, is a closet fan of Gudetama. Why not just use him?
- Runabouts: The little police cars were forgotten old mascots, but have been used a lot more often these days in collabs such as with Pop Team Epic and Love Live!. There could be another adult like Naoki, but one who was a fan of the Runabouts and lapsed out when they stopped producing merchandise only to come back when he sees them again.
- Chococat: As Chococat is still heavily merchandised in the West (outside of actual Sanrio stores), usually replacing Cinnamoroll or the Little Twin Stars, this one could be an Occidental Otaku to contrast Ryou's But Not Too Foreign.
