Big Wiggler

Mega Wigglers are a sub-species of Wiggler that first appeared in New Super Mario Bros. Wii. They are five times the size of a normal Wiggler (but they're not bigger than Super Mario Sunshine's Wiggler) and live beneath the ground near acid pits.

New Super Mario Bros. Wii
In New Super Mario Bros. Wii, despite being enemies, they can help Mario get items normally out of his reach. For this, the player must jump over a Mega Wiggler and press the 2 or A buttons to do a high jump, as if he were using a Spring.

Mega Wigglers cannot be defeated (even invincibility is rendered useless), and they'll hurt Mario by running into him. They can also defeat Swoopers. Also, they don't get angry if Mario jumps atop them.

Super Mario Galaxy 2
They reappear in Super Mario Galaxy 2 in the Supermassive Galaxy. They appear on the Stone Tube Planet, and Mario must avoid them to reach the Power star. One that appears in an angry state circles the tube towards the end. Nothing can defeat these foes. The Co-Star Luma will be able to stop them from moving and hurting Mario.

Trivia

 * Mega Wigglers were originally going to appear in New Super Mario Bros. However, a gigantic one appeared in World 7-3.
 * Through hacking methods, it is possible for Yoshi to eat a Mega Wiggler in New Super Mario Bros. Wii. This is one of two ways to defeat a Mega Wiggler; the other method requires Yoshi to spit out a fireball at it.