Singing along to an episode of Dora:
Maddie: Back-cack! Back-cack!
Me [realizing she cannot turn three still calling it a "back-cack"]: Bugaloo, it's pronounced back-PACK. With a P.
Maddie: Oh... Back-cack.
Me: No - with a P. Like Peter. Can you say Peter?
Me: Or like Peas. Can you say Peas?
Me: So try it with a P... back-Puh-Puh-Puh-PACK.
Me [laughing too hard to correct her again]: Um, sure.