I like to use ’I Can’t Believe it’s Not Butter’ on my toast in the morning, because sometimes when I eat breakfast, I like to be incredulous. How was breakfast? Unbelievable.

This line is a stand-up joke by comedian Demetri Martin, built around the branded margarine “I Can’t Believe It’s Not Butter.” Martin’s comedy style often leans on wordplay, literalism, and the collision of everyday phrases with their logical implications. Here he riffs on the product’s slogan as if it were an invitation to adopt a posture of disbelief (“incredulous”) at breakfast, then caps it with a mock review—“Unbelievable”—that echoes the slogan. While widely circulated online as a Martin quote, I can’t confidently pin it to a specific special, album track, or published collection without a verifiable citation.

The joke turns advertising hyperbole into a personal philosophy. By treating “I can’t believe it” as a literal emotional state rather than a marketing claim, Martin exposes how slogans smuggle exaggerated reactions into ordinary life. The humor comes from the mismatch between the mundane act of eating toast and the grand stance of incredulity, plus the final punch line that reframes a routine breakfast as something “unbelievable.” It’s also a compact example of Martin’s meta-linguistic comedy: he mines the gap between what words are meant to do (sell margarine) and what they actually say (announce disbelief).