The Born Loser - 2017-03-27
Brutus Thornapple, a man who appears to be in late middle age, with a largely bald head (save for a narrow band of hair stretching horizontally from ear to ear via the back of his head, and a single strand poking up from the top, near the back), wearing a black suit, white shirt, red bow tie, and brown shoes, sits at a table. One foot is on the floor, the other hangs in the air - his right leg is balanced across his left, perpendicular, so as to display the sole of his right shoe to the viewer. His left arm rests on his right shin.
The table is brown, apparently wooden, with four legs, and appears to have a round top. Most of the table is concealed by a white table cloth, which hangs nearly to the ground. The chair on which he is seated is the same colour as the table - presumably made of the same material - and of a fairly typical "dining chair" style, with four legs and a slightly angled back. The background is a pale green void.
Thornapple is holding a white teacup in his right hand, slightly in front of and below his face. There is a puff of steam floating in the air above the teacup. Thornapple appears to be looking in the reader's direction, breaking the so-called "fourth wall". His mouth is open as he addresses us, his audience, saying "There's nothing like a good, strong cup of coffee to get you going in the morning!"
In the second panel, Thormapple has moved the cup to his lips and closed his eyes. The puff of steam is gone, replaced by a single wisp. Thornapple is apparently taking sip of the beverage (implied to be coffee) presumably contained within the cup.
In the third panel, Thormapple has placed the cup on the table, near the edge closest to him. The single wisp of steam still floats above the cup. Thornapple's right hand is no longer visible, presumably hidden behind him. His eyes are still (or perhaps again) closed and his mouth is open once more as he is again speaking. This time, however, he looks disappointed (or perhaps resigned) as he says "Unfortunately, this is decaf!", the exclamation mark at odds with his dejected pose.
The joke, such as it is, sets up in its premise the expectation that Thornapple is currently drinking a good, strong cup of coffee - the implication being that a good, strong cup of coffee contains sufficient caffeine to "get [one] going". The punchline contrasts with both this implication and also with the appearance of Thornapple's face in panel two (which could be interpreted as a look of satisfaction) and, ideally, surprises us with the information that the beverage Thornapple is drinking is actually decaffeinated coffee, and therefore will not have the power to "get [him] going".
This joke follows a fairly typical scheme for generating amusement, which is to create expectations in the minds of the audience only to reveal that those expectations are unfounded. The audience is then pleasantly surprised to discover their mistake, and marvels at the cleverness of the joker in pulling off this deception. Specifically, we are led to believe that Thornapple is talking about the beverage that he is currently consuming, but in fact he was referring to some other, hypothetical beverage - one that he would prefer to be drinking, but is, for unstated reasons, not drinking.