Crimson Bloon

The Crimson Bloon is a Bloon Conception that first appears on round 31. It is a special bloon in 2 ways. First off, it is a parent of nothing and takes 3 hits to take out the outer (and only) layer. It is also special in that it stuns all towers within a 0-0 dart monkey's range, however this ability gets removed for half a second every time it is hit. It is also immune to many towers (such as the monkey ace & sniper monkey), which have infinite potential range.

Strategies
The crimson bloon is a really tough one to pop if your not prepared, as it is really effective against short-ranged towers and extremely long ranged towers. However, there are still many ways to pop it.
 * An effective way to take out these bloons is to make a 0-0 dart monkey barely far enough away from the track to make it not able to hit it. This will increase the range enough that the Crimson Bloon cannot stun it. Now, upgrade that dart monkey to 2+-X, however it is preferred to use 2-3+. Then, repeat. Doing several of these will make it nearly impossible for them to pass.
 * Super monkeys can make quick work of them, just be sure there not too close to the track.

Trivia

 * The Regrow Property does not effect Crimson Bloons, and in fact it can make it slightly easier to pop as it makes the bloon bigger, meaning that towers can attack it sooner. This can be exploited as past round 55, Crimson Bloons take the properties that the green bloon it replaced would've had, meaning it can replace regrow greens.