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The cat and the big man are trying to one-up each other by lifting progressively heavier weights. In the 8th panel, the bigger man struggles to lift a very heavy weight, but he lifts it. The Well-Meaning man offers to help, but ends up dropping the weight on his foot. Meanwhile the cat, unable to one-up the amount of weight the big guy lifted shifts tactics by claiming to be working on a novel. The redundant “actually” suggests that he isn’t really working on a novel, he’s just making an empty boast to save face.

The two jokes are 1) Cat is trying to preserve his ego by out of nowhere lying about novel-writing during a weight-lifting contest, which is silly, and 2) The well-meaning man offers to help the big man without really thinking through the consequences of his actions which, in this case, is to hurt his foot by dropping a weight on it. That’s really more of a Loony-Tunes style joke than a silly non sequitur like the first joke.