A few of his cartoons were controversial simply because they were hard to understand. A particular example was "Cow Tools," which depicts a cow standing by a table on which rest four oddly shaped objects. Larson had found it funny that cows would be really bad at toolmaking. His mistake was making one of the tools resemble a saw, as it led people to believe they had to identify the other tools to understand some kind of deeper meaning. "'Off days' are a part of life," he writes, "whether you're a cartoonist, a neurosurgeon, or an air-traffic controller."