It remains to be seen if anyone else will be on hand. But if more Super Mario characters are indeed lurking in the story, two in particular stand out as bosses likely to menace the heroes - Tryclyde and Fryguy.
The Super Mario Galaxy Movie's Super Mario Bros. 2 Tribute Is Missing Two Villains
Trailers for The Super Mario Galaxy Movie confirm that during their adventures, Princess Peach and Toad will enter a casino occupied by multiple Mario minions. There, they will incur the wrath of a crown-wearing frog creature named Wart and do battle with Birdo. Also in attendance during this sequence are Clawgrip, Mouser, and classic minions called the Ninjis and the Sniffits.
There's one thing that Wart, Birdo, Clawgrip, Mouser, the Ninjis, and the Sniffits share in common, which is their inclusion in Super Mario Bros. 2. In the 1988 NES gem. Mario and company go on a journey in the dream world of Subcon to defeat Wart, the main villain. Along the way, they have to get past through a slew of bosses, including Birdo, Clawgrip, Mouser, Fryguy, and Tryclyde.
Clearly, The Super Mario Galaxy Movie is gearing up for a major tribute to Super Mario Bros. 2. It has the game's main villain in Wart, two of its most common minion types in the Ninjis and the Sniffits, and three of its five smaller bosses. Given everything it's pulling from the game, it would be odd if the only two still-missing bosses - Tryclyde and Fryguy - aren't present too.
In The Super Mario Bros. 2, Tryclyde boasts the appearance of a three-headed snake. Serving as the boss of two different worlds, the fireball-spitting monster is essentially a much more powerful and menacing version of the Cobrat, a snake minion found in the desert levels. While avoiding Tryclyde's fireballs, the player has throw Mushroom Blocks at him to win.
Fryguy, on the other hand, is a sentient ball of fire conjured up by Wart. Being made of fire, he's immune to physical contact, forcing the player to throw Mushroom Blocks in order to inflict harm on him, not unlike the strategy that's to be employed in the fights against Tryclyde.
What To Expect From Tryclyde & Fryguy If They Appear In The Super Mario Galaxy Movie
From the looks of things, Super Mario Bros. 2 will be represented as a single area (the casino) in The Super Mario Galaxy Movie, allowing many of its key players to appear at once, presumably as underlings of Wart who will get to have a fight with Peach and Toad. Some could only be background Easter eggs, but it's possible some will get to take part in the action, not unlike the approach being taken with Birdo.
Birdo is shown using her signature ability from Super Mario Bros. 2 against Princess Peach. The game may do the same with Mouser, Clawgrip, Tryclyde, and Frygu, given each boss an opportunity to launch game-accurate attacks. If that happens, we may see Peach and Toad defeat them in ways that honor the games.
Neither may have voice lines nor meaningful roles in the story, but letting them participate in at least one battle in The Super Mario Galaxy Movie would add some great Easter eggs that pay tribute to the gameplay of a Super Mario classic.