- "A Cog Invasion has begun!!! [Cog name] has taken over Toontown!!!"
- ―Toon HQ
A Cog Invasion is an event that causes a specific Cog to invade a district. They may occur randomly, but tend to be triggered with the use of a Cog Summon. Toons will gain double experience points for gags when they defeat a Cog during an invasion. The length of an invasion is supposedly random with some factors such as Toon population of a district slightly changing the length of the invasion. Cog Invasions that last for a set amount of time, which can typically be up to an entire day or a whole weekend, are known as Mega-Invasions.
- Main page: Cog Summon
A Cog Summon is a reward which grants a Toon the ability to either summon a specific Cog, Cog Building, or Cog Invasion. They are granted by Bumpy Bumblebehr if the Chief Justice is successfully defeated. The rewarded summon is random, however, cannot be a summon that is already being carried. A Cog summon can be used by opening the "Cog Gallery" page in the Shticker Book, and clicking on a small button next to a Cog's face and selecting a summoning option.
Toontown Rewritten has its own Cog Invasion API, which provides an updated list of Cog Invasions by districts. The API, available in the JSON format, provides information about the invading Cog types (and also mentions if there is an invasion of Skelecogs or Version 2.0 Cogs), the size of the invasions, their progress, and the time at which the API, as well as the invasion data for each district, was last updated. The API allows retrieving the invasion data from other websites as well. If an error occurs, the API only returns the error.
As alternatives, players may visit Discord servers to keep track of ongoing Cog Invasions., or join either /r/ToontownRewritten or the official Toontown Rewritten
- The very first Cog Invasion consisted of Mover & Shakers, probably summoned by a member of the Toontown Rewritten Team. Since then, tens of thousands of invasions across all 32 Cogs have invaded every single district over the years.
- On May 26, 2014, the very first Version 2.0 Cog invasion occurred. Doctor Surlee addressed an emergency memo to the Toon Headquarters about his storm on Sellbot Headquarters with Lord Lowden Clear and several members of the Toon Resistance, telling them to signify a warning that Version 2.0 Cogs were taking over Toontown.
- Throughout the weekend of October 10, 2014, Toons gained triple instead of double gag experience points during invasions as part of Double Experience Weekend.
- As of 2015, Toons can earn double experience in a Cog headquarters regardless of an invasion.
- Invasions will time out after (0.7 * numCogs) seconds. This was confirmed by former Toontown Rewritten staff member, Jeremy (jjkoletar), during a Discord discussion in the early hours of January 2, 2020.