Your psychology teacher asks the class to name Franz Joseph Gall's hypothesis stating that one's personality can be determined by the bumps in their skull, and you automatically shout out, "PHRENOLOGY!" and grin, because you remember good ol' Fozzie Bear's phrenology demonstration on Kermit.
In settings where swearing is frowned upon, you exclaim, "What the Frank Oz?" or "What the Fraggle?" in disbelief.