More literal:
* Coquin malicieux: This translates literally as "naughty mischievous," capturing the playful but slightly troublesome aspect.
* Gamin espiègle: This translates as "playful kid," emphasizing the youthfulness and mischievousness.
More idiomatic:
* Petit filou: This is a more informal and endearing term for a "little rascal," implying a playful and harmless trickster.
* Loupiot farceur: This is a more playful and lighthearted term, meaning "playful rascal."
* Sale gosse: This is a less flattering option, meaning "brat," and implies a more annoying and disruptive rascal.
The best translation will depend on the context and the intended tone. For example, if you're talking about a charming child, "petit filou" would be a good choice. If you're talking about a playful but troublesome adult, "coquin malicieux" might be more appropriate.