These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
"Funny Aneurysm" Moment: Calvin, overreacting as usual in the 2009 episode "Invasion", claims that "Japan is going to fall into the ocean!" Two years later, Japan found itself at the mercy of the ocean.
Then there's "SouthWest Pacific", which is about Calvin performing in a school play. What does the title mean, then? Well, during World War II there was an area entitled South West Pacific, where many important things happened. The wartime definition for this? A theater.
Padding: Season 1 had a Running Gag where Hobbes would misinterpret something Calvin said or did, and Calvin would retort. The duo would then argue for a painfully long amount of time about something with no meaning to the plot. This has thankfully been phased out.note It should be noted that a similar chain of events was a Running Gag in the Hank the Cowdog series, which the author loves.
What an Idiot: Calvin attempts to fix a satellite dish when a tornado is coming.
The Woobie: Susie Derkins has the world against her in "Chains"
Dr Brainstorm in "Thunderstorm" considering he spent most of the movie trying to defeat his friend-turned-enemy who apparently betrayed him and rubbed his temporary victory in his face during the climax.
Socrates seems to be heading toward an arguable direction towards this in the final season.