2013 version: During the Stepsister's Lament, Charlotte has this to say about the Prince and was agreed with enthusiastically by the ladies of the court:
Yes, he's witty/So disarming
And I really like the way he holds the room
Clever, cunning/Ever charming
How do I make him see I'm special?
But from what we see of Topher, he's none of that. He's an awkward Adorkable dork, insecure and controlled by Sebastian re: state matters. He doesn't even feel like he fits in at the ball, much less "holds the room". Ella's the only one who gets that. She doesn't have to "make him see [she's] special", she already is, in his eyes, because she understands and empathizes with him - unlike all those well-dressed ladies who know nothing about Topher.
Calliope is the name of one of the Muses in Greek Mythology, while Minerva is the name of the Roman goddess of wisdom and handcraft. The stepmother is so obsessed with status and nobility that she literally named her children after celestial beings.
Several people have seen the 1997 version, or clips and pictures of it, and wondered how an African-European queen and a white king could have a Filipino prince for a son.
On a realistic level, this is simply what happens when you have a completely color-blind approach to casting, without regard for character relations. In-universe, though...
The prince tries the shoe on EVERY girl, including ones that don't even remotely resemble her, Calliope and Minerva notwithstanding. That is, girls who are clearly shorter or taller than her or of a different ethnicity. It would make sense if, say, Lionel went all by himself and forgot what she looked like entirely, but Christopher was with him.
It would have been pretty racist of him to have every black girl try on the shoe.