Character 1 is Min Min
Character 2 is Geno. His gimmick is that his neutral B causes Goombas to rain down. 1 in 20 Goombas wears a Geno hat.
Character 3 is Waluigi. His gimmick is that his neutral B summons small Piranha Plants in random locations. Sometimes they will do nothing, other times they will bite. Since his neutral B is RNG-based, you would expect his down B to also be RNG-based. But it's not. Unlike Peach, Waluigi always plucks a Bob-Omb when using down B.
Character 4 is Lickitung. Its gimmick is that its tongue homes in on you. No matter where you are. You could be on the opposite end of Great Cave Offensive and the tongue will still find you. When no one is playing as Lickitung, there is a 10% chance that the tongue will lick you anyway. Out of nowhere. You cannot escape it.
Behold, your next four fighters, in a clearly legit leak because it contains a Ken thumbs up: