"Big Time Rush" lead singer Kendall Schmidt has taken the phrase "man's best friend" to a whole new level -- by tattooing the face of his dog Sissy on his back ... and TMZ has the photographic proof.
Sources close to Sissy -- Kendall's adorable Boston Terrier -- tell TMZ ... the singer immortalized the pooch's mug onto the left side of his back a few weeks ago at Smith Street Tattoo in Brooklyn.
We're told the ink job took about an hour and was pretty painful -- but it won't be his last ... especially if he ever gets another dog.
'Big Time Rush' Singer
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8/14/2013 12:15 AM PDT BY TMZ STAFF
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