Who are the characters in the poster?

Ich don't think all those characters from way further into the manga would appear on the Key Visual of the first season of the anime.

I think the crouching person could either be Spitz or Winter. Grizzly-sensei still could be that one man on the right though. The sitting person looks kind of feminine, thus I would think of Dr Mofu or the reporter girl, because the other girls like Amamiya don't fit the body type or aren't really that important to the first season like president Eme ore Fin Fennec. The other guy could be Kawasemi (if I remember his name correctly), that police officer and old acquaintance of Amamiya, if we use the same logic of it being someone relevant to season 1.