When Jellybean was born, I became pretty adept at guessing ages of other babies, based on their size and what they were capable of. Then, as she became a toddler, I could look at other toddlers and gauge if they were younger or older, usually by how tall they were and how well they walked, etc. She has been very tall for her age since she started walking. It was a good lesson for me to have the super-tall kid, so that I didn't make too many assumptions about other people's kids at the park or play places.
L's brother is 6'7". I have heard L's mom talk since Jellybean was born -- and probably even before that -- about what a struggle L's brother had with always being the tallest kid. People, including his teachers, expected more from him because he was so tall. They would be out somewhere, and an adult or other child would ask him a question and be puzzled with his response. They didn't realize the child they were talking to was 2 years younger than they thought!
Jellybean has continued on the height trajectory similar to L's brother. Now that she is in preschool and interacting more with kids and adults, her height is affecting more and more situations. Even when other kids and adults know her age, they have trouble reconciling that a 3-year-old is the same size as a tall 5-year-old. Combining her height with her strong verbal ability makes it even more of a sticky wicket. Jellybean's preschool teachers have been very good at remembering her abilities, and she's in a mixed-age class, so all the children are accustomed to dealing with others of varying ages. I'd like to say I thought of that ahead of time and that's why we chose this preschool, but it's just luck.
Because I (obviously) have never had experience being "the tall kid," her height/age discrepancy is something I am working on being proactive with out in public social situations. We had an issue the other day of both a child and a mom getting frustrated at Jellybean for not comprehending a social situation. They were forgetting that she is not quite 4. It's easy to do.
So I'm experimenting with different ways to approach this and convey it to strangers, so as to avoid situations like the one the other day. I have a feeling it will be a process for years to come, unless her growth curve plateaus.