behold
Explanation
The Joke
In the first panel, a man is confidently explaining to a group of friends how he is pretty sure "string theory is wrong" and offering his opinions on how the economy should be run. His friends suddenly grab him and shout "We got you!" In the second panel, it is revealed that his friends were not actually interested in his opinions -- they set him up. They tell him, "You weren't at a bar, buddy, talking to your friends. It was a decoy date! You got sent to express all your facile opinions while we went to catch a movie!" They weren't really engaging with his pontifications; they were tricking him into monologuing so the rest of the group could escape.
In the final panel, we see a baby labeled "Doppelganger" with a party hat, implying the decoy that was left in his place at the movie was hilariously inadequate -- or that the friends created some kind of stand-in for him.
The Humor
The comic skewers the "bar expert" -- the person at every social gathering who holds forth confidently on complex topics they don't actually understand, like string theory or macroeconomics. The joke is that this behavior is so insufferable that the person's friends have devised an elaborate sting operation just to get away from him. Rather than confronting him about his annoying habit, they use his own tendency to lecture as a trap, knowing he will happily monologue to anyone or anything. The reveal that it was all a setup plays like a scene from a heist movie, elevating a mundane social annoyance to comic absurdity.