What we have here are two consecutive days' worth of Marmaduke, with exactly the same joke (Marmaduke has eaten all the Halloween candy). Ruling out the theory that these two strips are a part of a well-crafted, ongoing storyline about Halloween candy and Marmaduke and Marmaduke eating all the Halloween candy, there are only a handful of reasonable explanations for this:
1. Just as there's probably more than one guy drawing Marmaduke, there's probably more than one guy writing Marmaduke at this point. And none of them bother coordinating with each other, because who gives a shit? This seems rather plausible.
2. The strip is still written by Marmaduke creator Brad Anderson, whose senility at this point has taken on almost supernatural qualities. Anderson's signature still adorns each Marmaduke strip, augmented by his son/brother/life partner Paul's, but as Anderson is at least seventy five and as much as a hundred and forty years old, it's just as likely that all he does is sign the strips. And he needs someone to help him do even that.
3. The strip from 10/29 is a reprint from that same date a year or two ago, and the one from 10/30 had been turned in a couple of weeks in advance. It's not at all uncommon for Marmaduke to recycle jokes (considering the inherent limitations of the strip's subject matter and that its run since the Eisenhower administration I'd say it's absolutely vital); usually they try not to write the same gag twice in the same week but sometimes deadlines are missed and shit like this happens.
I yearn for the days when I wouldn’t even have been aware of something like this.