I'd tell you who our subject for tonight is, but you already know his name
Snorlax: Aside from the obvious similarities in girth, Byakuya and Snorlax serve common purposes: they impede those who would otherwise be able to attain their goals. By taking on responsibility as the group's leader, Byakuya's goal was to squash the hopes of anyone who wished to murder someone, but just like Snorlax, he was stopped in the end by a tiny man wielding a long, thin instrument.
Persian: If you recall, Persian was one of the Pokemon I put on the real Byakuya's team back when I was doing PokeRonpa 1. Fats Waller here has it as a representation of how he's masquerading as Byakuya, but his disguise only goes skin deep: just as the two only share one Pokemon on their teams, the impostor was only an imitation of Byakuya's looks, not his personality or attitude.
Zoroark: Zoroark is known for both its impeccable imitation skills (with its specialty being humanoids) and its fiercely protective nature, both of which Byakuya II share.
Ditto: Oh, come on. I don't even need to explain this one.
Smeargle: Smeargle's Sketch ability lets it imitate any move, which by extension lets it fill any role on a team, albeit not very well due to its low stats. This is similar to how Big Al manages to copy Byakuya imperfectly, with the irony being that even though he didn't make a great Byakuya, he was a better person than Byakuya could ever be.
Megengar: I actually had a bit of a hard time deciding on an appropriate Mega for the impostor, but eventually settled on Mega Gengar for its ability and its shiny form's familiar rotund, white appearance. Megengar's Shadow Tag makes it so that so long as it is in play, the opponent cannot escape or switch out their teammates, reflecting Byakuya's watchful eye during the security party he threw; minimizing the threat of murder by confining everyone to one space and barring their exit.
That's all for today, folks! Tune in tomorrow for I! Buki! Mio! Da!