Bed Time is an Advanced Power card in Bloons Card Storm. It allows the player to select an enemy Monkey with up to 30 Attack Power and remove it from the game permanently. It can be used on Monkeys with no Attack Power stat, such as Banana Farms and the Prince of Darkness.
It could be helpful to use it on Wizard Monkeys before they ramp up too much damage, but it may be better to save a Bed Time in case the player brings out another control card such as Jungle's Bounty Druid, or get more aggressive with swarms of bloons to overwhelm them.
Gwendolin's Heat It Up and/or playing on Game Night can protect Monkeys with exactly 30 Attack Power against a Bed Time.