My two and a half year old grandson lives with his mother. Her roommate also has a two and a half year old child, a daughter. A few days ago they were playing together and my grandson noting that his playmate's stomach was exposed ,took his forefinger and poked her belly button. She thought that this was great and they both had a laugh about it.
Sometime later his playmate raised her arms inviting my grandson to poke her belly button again. As he moved his forefinger toward her for a repeat performance, she suddenly lowered her arms, backed away and said, "No! I have a headache."