naughty but nice
Harmful, distasteful, or reprehensible, but still irresistibly enjoyable, attractive, or desirable. Sometimes hyphenated if used before a noun. Naughty but nice, this divine chocolate cake certainly won't do your waistline any favors this holiday season. This is one of best naughty-but-nice fast food restaurants in the city.
naughty but nice
reprehensible but irresistible. informal The expression, which often carries a sexual innuendo, was popularized in Britain especially as an advertising slogan for cream cakes in the 1970s.