Ooh! This so interesting! I really like the idea of Victor and Alice being in MLP: Friendship is Magic (I love that show!). :)
Maybe his cutie mark could be a butterfly sketched similarly to the one he drew at the beginning of the movie or a music note. When I first heard of you doing this, I couldn't stop singing the theme song in my head with the words changed around. XD

My Little Victor and Alice

I used to wonder what crossover pairings could be

Until you shared it’s magic with me

Awesome RP posts, tons of fun!

Well-written fanfiction and headcanon

Sharing ideas, it’s an easy feat

And crossover pairings make it all complete

You have my little Victor and Alice

You know you’re all my OTP

:)