Sponge Golem

Note that this does not exist in Minecraft, It's written purley as fiction

Sponge Golem or Spongeman (spongemen when pluralised) are Utility Mobs found in Water Springs, Caverns near Waters located in the Overworld and the Possible World. It can be spotted or Created. Since Sponge is in creative only you can use cheats to spawn him in Survival Mode. This Golem are 10x stronger and Healthier than a Snow Golem.

About
Spongemen are sometimes spawned with Armour (Especially Chained or Diamond) and they have the ability like an enderman to build anything. When they spot Pumpkins or Snow Blocks they will Pick it up to build a Snow Golem. They Destroy all Hostile Mobs (even Creepers, Witches and Ghasts) around them and if they can't reach them they jump high (since they can jump really high). They are tamed when you built them or if you give them Water splashed on the Floor near it or Giving it to Drink and they will follow you anywhere you go.

Building
Sponge Golem is created in creative mode and spawnable using cheats in any mode. To create him is like the same like Snow Golem but with Sponges instead of Snow Blocks. The Diagram above states how to build him.

Transportation
You can climb on their backs (like pigs and horses) and control them (like Horses). You can be able to ride their back and control them once they are tamed.

Trivia

 * They love Snow and Pumpkins, that's why they like to Spawn Snow Golem.