I love this shot because I really think Thulani was smiling in this photo.
Here's a shot of Tsavo and Thulani right after they were roughhousing. It's funny; lions play just like domestic cats. Stalking each other, pouncing on each other. It's really an awesome thing because you know you're seeing a side of them that many people don't get to enjoy in the wild. They're not the vicious, savage beasts as they're so often portrayed. Just like domestic cats who sometimes stalk and kill mice or birds, but then later are cute and playful, lions are no different. They can be extremely affectionate and playful. Wonderful animals.