Here's why:
* Mischievous is an adjective describing a playful, naughty, or slightly troublesome quality.
* Good is an adjective describing something positive or of high quality.
There isn't a direct noun form of "mischievous". You would need to use a phrase or a different word to describe the noun form.
Examples:
* Mischievous behavior: Describes the actions of someone who is mischievous.
* A prankster: Someone who is known for being mischievous.
* Mischief: The noun form of "mischievous" meaning playful troublemaking.
Let me know if you have any more questions!