- For the Bloons Tower Defense 5 map difficulty, see Impoppable Difficulty (BTD5).
An Impoppable MOAB Pack tile
Impoppable Difficulty is the most challenging tile difficulty in Bloons Monkey City, represented by 5 dark red dots, or 5 black dots in mobile. This appears on later parts of the map, and on certain Monkey V Monkey attacks. Most players can lose with bad defenses, so be prepared.
Impoppable tiles usually have bloon types and/or strategies that are very hard for players to counter with their current defenses. For example, if a player has recently started and can only hold back green bloons, a Ceramic tile will probably be labeled impoppable. An impoppable tile may be bumped down to a Very Hard tile when a player levels up. After a tile is rated as impoppable, its difficulty may be rated by the City Cash reward that the player would receive from it; the higher the reward, the harder the tile. For example, an impoppable ZOMG Tile near the center of the city might have a reward of 
440 and send the first MOAB on round 13, but another ZOMG Tile on the edge of the boundaries may also be rated impoppable, but have a reward of 750, and send the first MOAB on round 6. Knowing this is useful when fighting Tiles that are all impoppable to gauge each Tile's difficulty.
Table of times before no more Impoppable tiles
For this table, a certain level may be reached before a tile may no longer have any Impoppable tiles. All tiles can be marked Impoppable except for Red Bloon and Green Bloon tiles.
| Strongest bloon in certain type of normal tile | Level at which the type of tile no longer has Impoppable tiles |
|---|---|
| Red | N/A |
| Green | N/A |
| Pink | 3 |
| Black | 7? |
| White | 8? |
| Lead | 9? |
| Rainbow | 11 |
| Ceramic | 12 |
| MOAB | 20? |
| BFB | 21? |
| ZOMG | Never |
| DDT | Never |
| MOAB Pack | Never |
| BFB Pack | Never |
Trivia
- Black Bloons and White Bloons are marked as Impoppable at the start of the game.
- Pink Bloon Camo/Regrow Assault tiles are marked as Impoppable at the start of the game.
- Due to there being different types of Impoppable Difficulty, a Pink Bloon tile and a Z.O.M.G tile can both be marked as Impoppable at the start of the game (only for comparison, as ZOMG tiles are unlikely to be within view at the start of game)
- The word "impoppable" is a play of the word "impossible". This is made to make the difficulty's name more related into the game.
- Normally, after level 24 or 25, with the right towers and upgrades, all impoppable tiles should not be impossible to defeat anymore. However, many will still require an amazing amount of skill.
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