I remember once reading a story about a Mom whose little 2-year-old boy heard the f-word when her husband hurt himself or something. So she's at the grocery store or something, and he, testing out his new word, exclaims loudly, "F***!" Cue stares by the other customers. Mom, thinking fast, says loudly to the little boy, "No, sweetie, it's *truck*. Can you say truck?"
The fish tank thing reminded me of something last night. I took the girls with me to LittlePenguin's dance class. As we were leaving, they just had to stop at the fish tank and look happily at the fish in the aquarium. So you know, this is a regular aquarium, maybe 40 gallons or so, with a wide variety of small-ish freshwater fish.
LittlePenguin looks eagerly through the fish. "Mommy, are there any sharks?"
Me, laughing: "No, no sharks."
She looks disappointed, then presses up against the glass so that she can look into the little pretend wrecked ship (like the one in Little Mermaid where a shark appears). "I think I see one in here!"