A blue worm.
Isaac clenches his teeth with his mouth wide open, while his eyes quickly move back and forth.
Isaac's tears travel in sinusoidal (wave) patterns. Tears travel in the direction they were shot, regardless of the direction Isaac was moving. Increases Rate Of Fire by 1.
The width of the patterns is normally 1 square. If you are standing right between two squares and shoot, the width will become 2 squares and you will be able to shoot the enemies behind a rock.
- Technology - The laser beam curves in the same pattern as the wiggle worm with tears, widening the affected area nearly to Isaac's full body width. A second, darker laser appears, mirroring the first beam.
- The same applies to Sacred Heart, but to a lesser extent.
- Inner Eye - If shot while standing in a square, one tear will be fired as normal, and the other two will move in the normal wave pattern, seeming to circle around the middle tear. If shot between two rows/columns, two tears will be shot together and move in a wave pattern in one row/column, and the other tear will do the same in the adjacent row/column.
- Mutant Spider - The four shots all group together, instead of spreading.
- Bob's Rotten Head - Makes the head move in a wave pattern.
- Tammy's Head - Gives cardinal direction shot grouping.
- The Wiggle Worm was inspired by one of the shooting patterns from the NES game, Fester's Quest.
- The sprite for Isaac's mouth when the Wiggle Worm is picked up is identical to ???'s mouth.
- If Polyphemus is acquired and then Wiggle Worm, shots occasionally fail to oscillate.
- Paired with My Reflection, shot tears will be locked in its original axis; normally, when firing with My Reflection, tears will come back to Isaac, no matter what movement they have to go through, but with Wiggle Worm, these shots will only come back on a horizontal axis if fired horizontally, and a vertical axis if fired vertically.