One of Baby's uncles, my brother Matt, rides motorcycles. Baby is well aware of this and has seen him pull up or ride away on his motorcycle. Thus, she has come to associate motorcycles with Matt.
Whenever she sees a motorcycle, she will point to it and yell out, "Matt!" We tell her yes, a motorcycle just like Uncle Matt rides. I'm not sure if she thinks that every motorcyclist out there is my brother, or if she is actually making the comparison between them.
She's very observant, and has noticed that although bicycles do not make the same noise, they also have two wheels. Thus, whenever she sees a bicycle now, she will also yell out, "Matt!"
I don't think she's noticed skateboards yet...