Just last week I cited a sequence in Sally Forth that showed the characters being aware of the fact that they're in a comic strip. Today, the characters in Barney & Clyde did something similar. (click on the image below to enlarge)
The primary difference is the style of humor, and the payoff. With Sally Forth, the characters never address the reader directly, but it's clear that they're talking not so much to each other, but to the reader. In Barney & Clyde, the characters explain the concept of "breaking the fourth wall" and the payoff is that they then do so themselves.
I certainly enjoyed the joke. And, not that two instances make a trend, but I'm looking forward to other strips going meta!