This is Minae Noji's third TMNT role, having played Karai in Teenage Mutant Ninja Turtles (2014) and Tang Shen in Tale of the Yokai (2015).
Alopex is a mutant fox firstly introduced in the TMNT IDW comics.
When Splinter and the turtles are training, Master Splinter is using drunken boxing to defeat them