Hearing Charlie's continuous barking inside the house, Cassie sat down, stared in his direction, and refused to go on. It was cold and overcast, almost rainy, but there was no saying "no" to these two. They wanted to romp and roll, so into the back yard they went.
Considering their age difference (Charlie is 6, Cassie is almost 6 months), Charlie kept up the furious pace of play pretty well. After awhile, he was clearly starting to slow, though, and would lie down, making Cassie do more of the play work.
To change things up and keep it interesting, when Charlie lay down, sometimes Cassie would turn and walk away. But she'd go just far enough to let him relax and feel safe. Then she'd turn and, from a running start, pounce on him.
Though fewer, they had their quieter moments too, and they followed each other like shadows, rarely leaving each other's side.
Charlie's now happily and completely conked --- but by the window, of course, where he's sure to notice if she goes by again. :)