Crack on the Wall

Crack on the Wall is an Expert Track for BTD6, which is unlocked at rank 40 and requires beating 2 Intermediate tracks to unlock. On it, you can see a part of the word "Supercalifragelisticexpialidocious," with an S and an E highlighted in thick red. This defines the start and end of the track. Near the top, there is graffiti of "Bloons Rulz," which is blue. The blue words can be used as water to your advantage. "Lol, Waves" is actually a bloon boost. When the bloons are on it, they move 2x faster and have a +30HP health boost. On the track, you can also see a drawing of a MOAB. MOAB-class bloons on the loop encircling the drawing will get a 1.4x speed boost as well as +3HP/sec regeneration.

Trivia

 * This was actually made to be a sidewalk track, but who does graffiti on a sidewalk? This also explains the appearance of the footprint.
 * The idea of graffiti came from me seeing the trains near my area. Yes, there's a lot.