From the Super Mario Wiki
A Squiggler is a miniature, likely quite young type of Wiggler that first appears in New Super Mario Bros.. With three body segments and a head about twice the size as the other segments with a sprout on its head, this tiny Wiggler crawls around the perimeter of pipes. Unlike regular Wigglers, they can be defeated by stomping them or by using a fireball. Squigglers are only seen in World 7-A. Squigglers are cream-colored with a small plant on its head.
A single Squiggler appears in Mario & Luigi: Bowser's Inside Story in Dimble Wood. This Squiggler manages the Wiggler family farm. Bowser meets with it and the Squiggler seems friendly. Bowser, however states bluntly that vegetables are gross and that meat is better. The Squiggler reacts to this by saying that a healthy body does not crave meat and then hides behind a rock. It can last be seen during the Sliding Punch tutorial, where it can be found if the player tries to head south. Upon doing this, it asks Bowser if he can smash up the rocks blocking the shortcut out of the farm. In this game, Squigglers are mainly colored yellow instead of pale cream.