In a 'wife sits on lap story', perhaps they are reminiscing about old times. They might be looking through an old photo album together, and as she sits on his lap, they laugh at the funny memories from the past. It's a sign of their comfortable relationship.
One story could be when a couple was at a family gathering. The husband was feeling a bit tired and stressed from all the socializing. His wife noticed and sat on his lap, giving him a warm hug. She whispered kind words in his ear, reassuring him. It was a simple yet intimate moment that showed their strong bond.
It's generally not appropriate behavior in most social and relationship contexts. Sitting on someone else's lap, especially when married, can send the wrong signals and may make one's partner uncomfortable or jealous.
There was this couple. The husband was sitting on a bench in the park reading a book. His wife came running up and jumped onto his lap. But she misjudged the force and they both almost toppled over. They ended up in a heap on the grass, laughing uncontrollably.
You might also need to have a conversation with the friend. Politely express that such behavior is inappropriate given your wife's marital status. Maybe something like, 'I know you two are friends, but her sitting on your lap is not okay in our relationship.' And then, depending on their reactions, you can decide how to move forward. If they are apologetic and understanding, it's a good sign. But if they don't see the issue, you may need to re - evaluate the relationship with both of them.
I'm not sure specifically as I haven't read that particular fanfic. But it could potentially be about a moment of interaction between Annabeth and a character named Pervy, perhaps in a context within the world of the original story it's based on.