This could be one of those times when "you had to be there."
Or, it could be one of those times where you just need to indulge a mom who thinks her kid is super cute.
Isaac: Knock knock.
Mom: Who's there.
Mom: Banana who.
Isaac: Why did the Pink Panther walk?
Isaac: So he could go, (singing to the Pink Panther theme) du dant, du dant, du dant, du dant, du dant. Get it!! He's saying "dead ant," get it? Dead. Ant. (hearty belly-laughing)
Mom: Good one kiddo.
*Update: See comment section for more detailed explanation of why I thought this was so funny.