I've been to Platform 9¾ at King's Cross, where a luggage trolley seems to disappear into a brick wall. It's a place to have your photograph taken on the way to a school that doesn't exist. There is something rather appealing about making room for that in an otherwise ordinary day.
For this comic, I imagined a father who needs a reason to join the queue. His daughter is a convenient one, until she decides she would be quite happy to leave. I like the small awkwardness of that: having permission to do something you want, and still feeling the need to call it a favour.

Comic transcript
Panel 1. A father and his daughter wait beside the Platform 9¾ photo spot. He looks towards the trolley and holds his phone by his side.
Dad: "We're only queuing for your photo."
Panel 2. His daughter points away from the photo spot.
Daughter: "I don't mind if we go."
Panel 3. The father hands his phone to his daughter beside the free trolley.
Dad: "We've waited. We should take one."
Panel 4. His daughter holds up the phone. The father grips the trolley and poses with one foot raised, as if setting off through the wall.
Dad: "Get the whole trolley in."
The wall sign reads "PLATFORM" and "9¾" throughout.