The Yerushalmi Pesachim 68b says:
האוכל מצה בערב הפסח כבא על ארוסתו בבית חמיווהבא
(One who eats matzah on the eve of Passover is like one who has intimate relations with his bride-to-be in his [future] father-in-law's home. )
As legend has it, Achad Haam provided the perfect rejoinder. He is said to have quipped:
Asiti shnayhem v'aynam domim.
(I've done them both, and they are not similar.)