From the Super Mario Wiki
Mega Wigglers are a sub-species of Wiggler that first appeared in New Super Mario Bros.. They are five times the size of a normal Wiggler, but they are not bigger than Super Mario Sunshine's Wiggler, and live beneath the ground near acid pits.
 Super Mario series
 New Super Mario Bros.
A Mega Wiggler appeared in World 7-3. Mario or Luigi has to ride on the Mega Wiggler through the entire level while avoiding enemies and obstacles. This Mega Wiggler is even larger than average Mega Wigglers.
 New Super Mario Bros. Wii
In New Super Mario Bros. Wii, despite being enemies, Mega Wigglers can help Mario get items normally out of his reach. For this, the players must jump over a Mega Wiggler and press the or button to do a high jump, as if they were using a Spring.
Mega Wigglers can hurt Mario by running into him while on their preset paths. They can also defeat Swoopers, along with most other enemies upon making direct contact. Also, they don't get angry if Mario jumps atop them.
It should also be noted that the Mega Wiggler is one of the very few enemies who can not be defeated by the Super Star power-up.
 Super Mario Galaxy 2
Mega Wigglers reappear in Super Mario Galaxy 2 in the Supermassive Galaxy. They appear on the Stone Tube Planet, and Mario must avoid touching them to reach the Power Star. One that appears in an angry state circles the tube towards the end. They can't be defeated, but the Co-Star Luma is able to stop them from moving and hurting Mario.
 New Super Mario Bros. U
 Mario Kart series
Maple Treeway makes a reappearance in Mario Kart 7, and so do the Mega Wigglers.
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