The Amalgamates are special entities from the Nintendo Adventure Book Monster Mix-Up. They were created using King Bowser Koopa's Monster Mixer device. Their appearances vary wildly, but seem dependent on their constituent creatures.
These creatures rise when a Goomba becomes fused with a Boomerang Brother. They resemble a Boomerang Brother from the waist up, but their legs are disproportionately small, a trait from their Goomba half which prevents them from moving fast.
These monsters rise when Chain Chomps become fused with Munchers. They have leafy stems as chains. Their aggressive personality is amplified by the fact that their ingredient creatures are also aggressive, which makes them dangerous.
These critters resemble a Goomba, but they also have a Koopa Troopa's head, hence their name. Their leaders are two of them called Goomby and Foomby. Goomba Troopae have a special weapon that mimics them: the Goombomb.
Goomba Troopae are created if Koopa Troopae are combined with Goombas.
Soopa Koopa Paratroopa
When three Koopa Paratroopae are combined, Soopa Koopa Paratroopae can form. They look like ordinary Koopa Paratroopae do, but Soopa Koopa Paratroopae have three heads, one for each of their constituent Koopa Troopae. Their strength makes riding them easy, too.
BOOM BOOM ON FAIAH!!
Boom Boom experiences the Monster Mixer because he ditches his Fortress-guarding duty and leaves Elmo in charge. His boss, King Bowser Koopa, tosses him into the machine with a Fire Snake, but Boom Boom survives and his head bursts into flames, so he tries to get water. Bowser takes advantage of this and states that Boom Boom is the hottest Koopa.
This amalgamate is the only one that splits some time immediately after it was created. It is the only one to have a dominator, who Boom Boom is. This is akin to the Mixes from Mixels, albeit uncontrollable as Boom Boom gets hurt.
This entity is born when King Toadstool and Elmo are finally fused together. He has King Toadstool's head and the body of a Koopa Troopa. While his constituent beings are rather dumb, the King Troopa apparently is smart. The King Troopa helps his liberators solve puzzles, but Mario does not trust him at first...