Nice and Moist
Over the 10-year run of Calvin & Hobbes, there is only a single occurrence of an established character celebrating a birthday (or, indeed, any milestone marking the passage of time). This takes place near the end of January 1987, during a week-long arc in which the eponymous duo attends Susie’s birthday party. As you may suspect, Hobbes’s presence in any group setting is liable to create fodder for Tiger Tracks, and indeed, a minor controversy does erupt during this event which warrants scrutiny.
The strip published on January 29th starts with Susie handing out plates in preparation for serving cake and ice cream (in my own opinion, cake and ice cream requires a bowl rather than a plate, but that is an argument for another day). During this prelude, Calvin confesses to Hobbes his fear that Susie picked one of those offbeat cake flavors that are generally regarded as undesirable to the general population, such as coconut—a fear that, knowing Susie, is not unfounded, though in my headcanon her favorite is a less-divisive red velvet.
However, Hobbes confirms that the cake is, in fact, chocolate—much more appropriate for a party. Yet this raises the question: how in the world does Hobbes of all people know what flavor of cake it is? Calvin asks as such, but before Hobbes can respond, a shout goes out:

The discovery of the missing slice of cake and Hobbes’s description of it being “nice and moist” is a strong indication to the reader that Hobbes, in fact, is the cake-cutting culprit. How could he know the texture of the cake without tasting it himself? This seems like an open-and-shut case. But is it?
I’m not interested in arguing about how Hobbes knows what. The flavor of cake is never revealed to the audience by anybody but Hobbes; and since his entire existence is in doubt, we can’t assume that his claims are necessarily true. That cake could just as easily have been vanilla. Were this the case, perhaps we’d find ourselves wanting to understand why Calvin comes to believe the cake is chocolate when it actually isn’t, but that would be an example of not seeing the forest for the trees. The question we should be asking instead is: if Hobbes didn’t preemptively sneak a slice of cake, then who did?
Suspicion immediately falls upon Calvin. The strip’s been running for a year and a half at this point. We know his game. We’ve seen how impulsive he is, how he prioritizes short-term reward over long-term consequences. And I’ve argued extensively that he is quick to assign blame for his own actions onto others—most commonly, Hobbes. Calvin is the clear and obvious culprit.
And yet… I can’t bring myself to believe that Calvin cut that cake.
To be quite honest with you, if you review all the strips from this week-long arc, this just might be the most well-mannered Calvin we’ve ever seen. He’s on his absolute best behavior. I know this sounds entirely unbelievable; this is Susie’s birthday party, for crying out loud! This should be prime time for mischief and hijinks! But that’s not what we’re shown. To illustrate my point, let’s go through the other strips in this arc leading up to the incident in question:
Day 1 — Calvin and Hobbes walk down the sidewalk on their way to Susie’s house. Calvin carries a neatly-wrapped gift, revealing that it is a bike horn—a token gesture, perhaps, but it is at least an agreeable and inoffensive offering. Although he contemplates skipping the party and keeping the horn for himself, he goes through with this act of social obligation anyway.
Day 2 — Susie greets Calvin at the door and invites him in; Calvin presents the gift and politely wishes her a happy birthday. Susie sees that Hobbes is wearing a tie and gushes over how cute he is. With mild annoyance, Calvin acknowledges that Hobbes was correct about how positively the tie would be received; though it’s interesting to note that, if Hobbes is indeed an inert stuffed toy as this series posits, Calvin must have taken the initiative to dress the tiger himself, displaying additional thoughtfulness toward Susie.
Day 3 — Susie announces a scavenger hunt will be played as a party game. The first item on Calvin’s list is an old license plate. Fortunately, Calvin already knows where one can be found and heads there immediately… where he begins removing the license plate from a car parked nearby. This act represents the height of his misdeeds this week, and while it does demonstrate a lack of civility that I don’t support, I have difficulty pinning the entire blame on Calvin for this one. I say this because some dunce (Susie, most likely) thought that old, abandoned license plates were items that would commonly be found laying around the neighborhood and could reasonably be found and collected by multiple kids (along with a list of other items) within the span of thirty minutes as part of a competition. Of course somebody was going to try yanking a license plate off of a car. Calvin might not even be the only one who attempts this. Really, just a surprising lack of foresight on Susie’s part.
The incident in question then occurs on Day 4. Here’s it’s worth noting that, as Susie hands a plate to him, Calvin is sitting calmly and politely thanks her. He’s not griping about being bored or having a bad time or anything. Had there not been a slice already cut out of the cake, the party may have concluded without any incident at all.
Still not convinced? That’s fine. Because our most definitive piece of evidence comes from Day 5:
Look carefully. As she thanks Calvin for attending and for the gift, Susie’s expression is perfectly pleasant (as is Calvin’s, for that matter). And that’s what’s so odd; because normally when these two characters part company, at least one of them is disgruntled or bears some ill-will towards the other. But there’s no resentment on Susie’s part here. Not even so much as a hint that she suspects Calvin ruined her party but just can’t prove it. She has been the victim of Calvin’s antics more often than most; she should know better than anyone what this kid is capable of and always approach him with an ounce of suspicion.
Despite the defilement of the birthday cake, none of those feelings are present here. For once, Susie was glad for Calvin’s company. As such, there’s only one conclusion we can draw from this: she already knows who the perpetrator is, and it isn’t Calvin. We may never know who actually ate that slice of cake, but if Susie isn’t accusing Calvin of the deed, it can only be because she knows with 100% certainty that it was somebody else.
Following that logic, if Susie has already identified the culprit, then it can’t be Hobbes either, as suspecting him would require Susie to believe that he is sentient. It goes without saying that this interpretation of the dynamic between Susie and Hobbes is preposterous and unworthy of consideration.
…Er. Probably.
Verdict: I guess I’m going to have to re-read the entire strip with this new “Susie is a Hobbes truther” theory in mind now, just to make sure.