A mischievous imp? Someone small and somewhat clever in the midst of causing small but somewhat clever trouble, I would think. As an aside, that little phraselet isn't vintage slang. It isn't even slang. It's just words. Look 'em up!
An example of an imperative sentence is "Please close the door." This type of sentence gives a command or request and often includes a direct address to the listener. Imperative sentences typically omit the subject, as it is understood to be "you."
An imperative sentence is a type of sentence that gives a command, instruction, or request. It often starts with a verb and may or may not include the subject, which is typically implied as "you." For example, "Close the door" and "Please pass the salt" are both imperative sentences. They convey a directive rather than a statement or question.