Crafty rascals is an evocative phrase that brings to mind a certain type of mischievous, cunning personality. There are a variety of synonyms that can be used to denote this type of behavior, each with its own unique connotations. For example, one might use the term "schemer" to describe someone who is constantly devising new plans and plotting their next move. "Trickster" has a similar meaning but implies a bit more playfulness and less malicious intent. "Conniver" suggests someone who is willing to manipulate others for their own gain, while "weasel" implies sneakiness and a lack of moral fiber. Ultimately, the choice of synonym will depend on the specific traits being emphasized.