Can you tell Stork from butter?

The question plays on the well-known “Stork” brand of margarine/butter substitute and the everyday act of judging foods by taste or appearance. Used as a teasing challenge, it implies a test of discernment: can you reliably distinguish the real thing from an imitation, or are you being fooled by branding and expectation? In a broader sense, it can function as a metaphor for critical judgment—separating authentic quality from substitutes in matters of taste, truth, or expertise. Because it is phrased as a casual, colloquial question, it likely circulated as an advertising catchphrase or a popular saying rather than a literary line.