Well, it has happened a few times this week. Early in the week, Maddie was overlooked and Kat was put on the floor. A back was turned and when we looked next, they were nose to nose.
They got along remarkably well. Maddie wants to lick Kat's face. I think the runny nose contributes to that. Kat wants to grab handfuls of Maddie's fur. Fur is soft and, well, furry. Since that evening, we have let them both loose and watched them closely. Since Maddie doesn't like to have her fur yanked, she tends to stay just out of arms reach. Maddie will stay close enough that she can get the pink tongue on Kat's hands and face periodically.
Maddie staying out of reach motivated Kat to learn to crawl. The first time I saw her crawling, she was chasing Maddie. Kat would take a step, Maddie would step away. So Kat takes another step closer to Maddie, who moves another step away. OK, it isn't the fastest crawl you have ever seen, but it is a start.
The same night Kat crawled, she also pulled herself up to standing in her crib. Wife had set Kat in crib and went to make a bottle. When she came back, Kat was standing in the crib, looking out through the bars like a little Konvict Kat behind bars. She has pulled herself up several times since then.
She is growing up and getting mobile. We will need to childproof the house soon.