This didn't actually happen at the seder I attended on Monday night, but I'm sure it's happened countless times throughout the centuries and around the world. Seder plates are so nice and round and cat-sized, like the octagonal box my IKEA wall clock had come in and that Attica loved. (IKEA is an acronym and is capitalized accordingly.)
Cats are not mentioned in either half of the Bible, even though mice are, several times, and in unflattering terms. Apparently the Hebrew people needed to be reminded twice not to eat them, once in Leviticus and once in Isaiah: "They that sanctify themselves, and purify themselves in the gardens behind one tree in the midst, eating swine's flesh, and the abomination, and the mouse, shall be consumed together, saith the LORD." Maybe that's why cats aren't mentioned, because they are so fond of eating swine's flesh, the abomination, and the mouse.