Bonus Bloon

The  is a special kind of bloon that can show up at any time in the game (from round 50 and on). It has no health or speed, but it doesn't move along the path. Instead it slowly fades in at any position in the screen, stays for 3 seconds, and fades out (takes 3 seconds to fade in and out). When it shows up, the player can click the Bonus Bloon, popping it, and receive a special reward, out of these:
 * Cash Prize: Gains $500-$2500 (depends on current round, reward maxes out at round 150). (50% chance)
 * Life Prize: Gains 1-10 (depends on round, reward maxes out at round 150, rounded to the nearest whole number, rounded up is result is X.5). (30% chance)
 * Item Giveaway: Pops into 15 random Usual Items. (50% chance)
 * Item Reward: Pops into 10 random Common items. (40% chance)
 * Item Prize: Pops into 5 Uncommon items. (30% chance)
 * Item Jackpot!: Pops into 3 Rare Items. (15% chance)
 * Bloon Ambush: 500 Green Bloons pop out of the Bonus Bloon and go towards the track. (25% chance)
 * Bloon Jackpot: 5 Slot Bloons pop out of the Bonus Bloon and go towards the track. (15% chance)

Trivia

 * This is a reference to the Golden Cookie from Cookie Clicker, but I didn't get the idea from it.
 * The image is a reference to the Bonus Sections in CB games (designated by a yellow ? on a green background).
 * For programming purposes, the reward is calculated randomly, with the chance meaning the chance that the currently "selected" reward will be awarded, if not then select another random one.