Inverted Middle-Seat. The "ghost" (doesn't have to be a ghost, just ignored/unnoticed) tries to get the attention of the other two players while they play through their own scene. The ghost can be silent or can speak. It may be easier to play a silent ghost, but spoken could be fun too.

Get players to focus on giving and taking while staying present in the scene. Teach players ways to draw attention. Show players that little moves can be amplified into big front-foot moves when you have the support of the other players.

Potential Problems:
If players don't find a way to explain why they're ignoring/not noticing the ghost early on, the scene might struggle to grow.