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Impish
Playfully Troublesome
Use 'impish' when someone causes mild trouble or irritation but remains endearing or likeable. 
Innocent Charm
'Impish' often carries a notion of innocence, unlike 'naughty' which might imply a bit more intent. 
Subtle Humor
An 'impish' action or remark is usually subtly humorous, not obvious or slapstick comedy. 