Helpfully labeled, because even I can't remember all their names half the time
Yes, Bowser's often-forgotten offspring are returning to harass Mario and Co. for this game. There aren't any pictures or videos of the fights online to my knowledge, but according to a preview on 1up the fights are similar to the Kid's Super Mario Bros. 3 experience, with a slight twist. In the fight with Iggy for example, he still bounces around on his ball and shoots stuff out of his magic wand, but parts of the floor will rise and fall. And before the fight even begins Kamek from Yoshi's Island shows up and ensorcells the room, which changes the floor to ice.
Basically what I'm trying to say is the boss fights sound like they're going to be crazy awesome.
While the inclusion of the Koopa Kids in any new Mario game makes is 100 times more awesome (it's worth noting that the only other recent game to use them, Mario & Luigi: Superstar Saga, was also awesome), it also fixes one of the big problems with the original New Super Mario Bros. Namely how the reoccurring antagonist role fell solely in Bowser Jr., who in addition to being a less interesting character design was also incredibly boring to fight.
This raises the inevitable lingering question: are the Koopa Kids supplementing Bowser Jr., or replacing him?
Does anyone care if it's the latter option?Story via Retronauts
Picture via Brandokay Productions