Quantity is its own quality.
Cannon Fodder are an infantry unit which replaces standard Grunts in Yapyap THE DESTROYER'S army. They are unarmed, excitable, and poorly trained, but free: they cost no resources to deploy [just takes time and population cap]. Though each unit is not exactly a powerhouse combatant, the Grunt Swarms are very useful for scouting, overwhelming enemy positions, and capturing points. In addition to standard infantry upgrades the Swarm can be trained in ancient Unggoy art of being Anklebiters, which gives them a weak close—combat capability and ability to dogpile the enemy and slow them down. Yapyap can also get them fired up with his Refer a Friend upgrade, which gives the unit a self—heal by packaging his best—selling novel on Grunt leadership together with some bandages.
An endless horde of overzealous Unggoy, ready to be marched into battle at a moment's notice! As Yapyap has lost [he says "misplaced"] more Grunts in their revolution than were even carried to the Ark in the first place, it's a bit of a mystery where these recruits are coming from. All that anyone knows for sure is that Yapyap THE DESTROYER argues with his Throne of Woe, gives it a few good kicks, and glassy—eyed reinforcements show up at camp the next day, ready to fight for the glory of Yapyap! In these dark days Grunts adrift are a gift, so other Grunts don't ask any questions.