A gag barrel is an item found in cog facilities. The Toon Resistance put these barrels there. These items are obtained to restock gags. They turn dark when they are used by a toon. They can usually be obtained after fighting cogs or manuevering obstacles. The gag they restock can be seen on the image of a gag that it has printed on the barrel.
The gag barrel does not make an appearance in Cog Golf Courses because gags can be obtained instead by winning Cog Golf games.
In the Sellbot Factory, the gag barrels' logos are levels 1, 3, 5, and 6, whereas in the Cashbot Mint and the District Attorney's office, they are only level 6.
If the toon gets a gag barrel but does not have the selected gag, then it will fill up the next highest gag (or the next lowest gag if the barrel shows a gag that the toon does not have enough experience for.)