I don't have any kids but I have two nieces who are (almost)5 and 6.

The 6 year old is very active and we have a ton of stories on her anything from her calling parks "parking lots" to her deciding that petting zoo goats were made to ride on.

The almost 5 year old is a lot less active but is very strong one of my fondest memories is from 2 summers ago (we only get to see them in the summer thanks to a nasty divorce that ended badly for the girls and my brother) so they were 3 and 4 the 4 year old and the almost 3 year old were playing with a Radioflyer wagon taking turns pulling each other. The older one pulled first and strained under the weight of her little sister who is actually about the same height and weighs several lbs more. That was a pretty funny sight on its own. She got the younger one pulled about 6 ft and fell down and said she died. Then the younger one said "my turn!" so they switched. Apparently they both decided that pulling was more fun than being pulled. They fought over who pulled and with the 4 year old kicking and screaming to be put down and the 3 year old carried her to the wagon set her inside and started pulling down the gravel road with very little trouble.