Ask Jessie if she wants a penis.
From Create Your Own Story
"Did you want to grow a penis."
Jessie shuffles her feet. "I guess not. But I'm curious. I've seen Timmy's in the bath and I've touched i-"
Jessie stops herself and looks away, immediately starting to blush by admitting such a naughty thing to you. You smile and take her chin in your hand, reassuring her. After a moment she continues.
"Umm... but you say they get bigger? How much? I can't imagine Timmy's growing more." You nod. Your son was already fairly well endowed for his age.
Staring at your adorable young daughter holding her towel around her drying skin you just can't help yourself.
"Well I can show you."
Jessie's eyes open wide with excitement. She is most definitely interested. Her hands twist her towel.