The top Instagram picture of 2013 (in terms of likes) was not just a celebrity, but two of them unlikely paired together: Will Smith and Justin Bieber.

Smith, looking both youthful and old with his Fresh Prince era flat top haircut, generous biceps, grayish beard, and facial lines, has his left arm over the teen idol's neck and his right hand in a peace sign. (Is that a smartwatch on his left wrist?) Donning a typically plain top (the better to show off his sleeve and pharaoh medallion), Bieber's right arm is around Smith's back, and he's giving one of those teenage/adolescent looks into the camera as a sort of rebellious replacement for a traditional smile or Smith's go-to, no teeth grin. The picture attracted 1,496,070 likes, most of those on the basis of Biebers 12 million plus Instagram followers and 47 million Twitter devotees, according to today.com.

The combination of Smith and Bieber isn't as odd as it may seem. A few decades ago, Smith was the precocious musical prodigy until he put most of his focus into acting. Jaden Smith, the 45 year-old's musically inclined teenage son, appeared on Bieber's 2010 track, "Never Say Never" (not a bad song actually). And then there's the way of Bieber, 19. Despite his seemingly lack of street cred (from an outsider's perspective), he mingles with stars from all over the musical industry and seems to gain most of their approval.

The photo's popularity may have been further spurred by Smith's appearance on the Graham Norton show earlier this year. As Bradley Cooper and Heather Graham helplessly looked on, Smith, his son, and Prince friends Carlton and DJ Jazzy Jeff re-enacted famous musical scenes from the 1990's sitcom. That YouTube video has nearly 20 million views (see below).

Instagram also released its most popular hashtags of 2013, only two of which are unique to this year (not in order), today.com reported: #love, #friends, #selfie, #tbt, #fashion, and #food.