sly dog

"Aren't you the sly dog," she said with a grin.

He turned to his wife and said, "You see what the sly dog is doing?

His principles were those of a rather sly but very high-class and exclusive dog, neither better nor worse.

A sly dog, that one.

But as it turns out, a sly dog as well.

Had the sly old dog been plotting defenses while hanging around the gym?

He likes to play jokey pranks, but he is also a sly, hard-biting dog.

Heron, however, nudged him expressively with his elbow and said: --You're a sly dog.

But I'm afraid you're a sly dog.

A writer from E4.com described Doug as a "charming fresher with a dark past" and a "sly dog" for dalliances with two female students.