"Thank you sir," says the squaddie who puts my bags through security as we enter the Olympic Park.
"And can you tell me what the second largest land mass in the world is, please?"
A slightly unusual question to be asked at a stringent security point but the positivity and good-naturedness here at the Paralympics is infectious and so, six days in, it feels like an entirely normal conversation to have.
"Is that Antarctica? Or Russia?" I reply.
"It's neither of those," says another army man, taking another bag out of the machine. "And that's not in the rules."
"Antarctica doesn't count," explains the first fella, "it's not populated."
They keep their geography game going, involving park-goers to boost their spirits. "We'd go crazy otherwise," the men who aren't G4S tell me.
From the moment you leave Stratford train station, through the entrances and into the park, everyone is happy, pleased to be there, and the Games-makers shout "Hello," and "Are you enjoying yourself?" almost every step of the way.
It's like America has come to Britain and turned British - well, you think of a better way of putting it if you can.
The morning motivational group hug from the park's Coca Cola beatbox crew
I think this is what David Cameron was talking about when he said he wanted to harness the positivity of the Games and I'm not sure it comes across on the TV.
Though I didn't come to the Olympics, I'm assuming the big difference is the number of disabled people here.
Disabled people rarely have a reason to come together and mostly don't really want to - quite apart from the accessibility logistics.
I come down from East Anglia on a commuter train and usually plonk myself in the disability seat, let my guide dog stretch out in the space designed for a wheelchair to go, and fall asleep.
But now there's not just one wheelchair coming in, there's a small handful.
At Stratford I keep hearing the station staff's radios crackling into action with phrases like: "I'm just meeting a wheelchair at platform 10," and "a mobility impaired person is arriving on platform nine in five minutes, can someone get there please?"
Everyone is joining together to make these Games positive and fun and it's working.
Except perhaps for the brothers we saw yesterday. Question: if you were a powerchair user and your little brother kept prodding and pestering you, what would you do?
Yes, that's right, follow the example of our man - reverse your chair, turn, aim and, at top speed ... run over him.