Helio-grubs are creatures in Quest for Booty and All 4 One, with a cameo in the 2016 re-imagined Ratchet & Clank game and movie. They are small, glowing green, grub-like, insectoid creatures with two yellow eyes on stalks, a turquoise stripe down their faces, small but sharp teeth, and four small claws around for legs. They are most notable for glowing in the dark. This makes them usable as a makeshift flashlight, and allowed Ratchet to pick them up with his OmniWrench. They have appeared on planets Merdegraw, Igliak, Magnus, and Veldin.
Helio-grubs have a large gameplay role in Quest for Booty. Ratchet can pick them up from small pools in the caves with his OmniWrench Millennium 12, allowing him to explore the dark Morrow Caverns, as well as to scare off creatures such as the thwogs which are afraid of the light. They cannot be thrown.
In All 4 One and the re-imagined Ratchet & Clank, helio-grubs do not have a gameplay role. In the former, several are found as power sources for lights in Luminopolis on planet Igliak and throughout Dr. Croid's Croid labs, but cannot be interacted with. In the latter, Ratchet picks up a helio-grub when inspecting Clank following a crash, but in gameplay, they are larger than in Quest for Booty and cannot be interacted with, as hitting them with the wrench will simply knock them away and cause them to splutter into a puddle of green slime.