Squiggler

From the Super Mario Wiki

A Squiggler resting.

With three body segments and a head about twice the size as the other segments with a sprout on it's head, this tiny Wiggler crawls around the perimeter of pipes. Squigglers are only seen in Level 7-A and are obviously the baby versions of the Wigglers. It can be inferred that they are born in pipes. When they mature enough they (presumably) become a Wiggler, then a Flutter.

[edit] Trivia

• If Mario or Luigi jump on a Squiggler, neither of them will get points. However, if one of the brothers Ground Pound on it, points will be earned.