Side Effect is a macroscopic, turquoise, unicellular alien. He has multiple organelles inside his cytoplasm, and 3 flagella on either side.
The Omnitrix symbol is located on the upper part of his cytoplasm.
- Sickness Induction- Side Effect is able to attach to a compatible host's body, causing them to become ill. The symptoms differ greatly depending on the host's species, but most of the time they cause discomfort to whoever is infected by him. He is able to control the strength of the ailment's effects.
- Ally Undermining- Side Effect causes any transformation he is attached to become weaker, making him mostly useless in combat.
- Immune Hosts- Side Effect is unable to affect any energy-based or mechanical species.
The Gesiifluenza are a parasitic bacterial lifeform that lay dormant deep within the cold center of "ACH-00". ACH-00 is a comet comprised of an extremely resilient rock that is covered in a thick layer of ice. This travelling celestial body has an as of yet unknown origin, but is known to drift throughout the Milky Way Galaxy. Upon passing by solar systems with enough heat, chunks of ice will break off from ACH-00 and gravitate toward nearby planets. Once in the thermosphere, the ice will melt and awaken the Gesiifluenza - dispersing them throughout the atmosphere. After finding a suitable host, the Gesiifluenza will inflict on them an immediate illness. Depending on the species, this could be a passive symbiosis or cause adverse effects.
- Side Effect is part of the Omnitrix's Parasite Playlist, being able to make other transformations fall ill.
- If Side Effect attaches to Heatblast, his pyrokinesis becomes cryokinesis, with his flames becoming blue in color.
- Side Effect and FleaShooter were based on transformation concepts that appeared inside the Parasite Playlist in the video "What if Venom was a Ben 10 Alien?" from The Ink Tank channel on YouTube.