Two-in-one

My Father, in the car:

"I was writing (...) about this thing that happened to me back when I wrote the book, History Of The Chilean Socialist Party. It was the Party's 49th anniversary so for the fiftieth there was a big celebration. Allende was in power, the party was strong, it was held in the Estadio Nacional. It wasn't full, but almost. People were going around selling my book, carrying whole baskets of it. I was sitting there in the stadium and two guys came to me, with the baskets, offering to sell me my own book. I said,
'No, sorry.'
'Why not?' They asked.
'Well, I'm one of the people who wrote the book.'
They went quiet. Then they looked at each other and went away. As they left, one of them turned to me and said,
'Nice excuse you came up with, bullshitter.'
It was the shortest and strongest critical commentary I've received in my life."

Later:

Him: "So, need anything from the supermarket?"
Me: "Actually, i think i need a new toothbrush."
Him: "Ok, possibly one with a different color from mine."
Me: "Yeah, for months i've suspected we've been using the same one."
Him: "Another thing that bothers me is, how come there's three of us at home but there are always four toothbrushes in the bathroom?"
Me: "You're right!"
Him: "I'm starting to suspect there might be someone hiding in the house. Somebody who creeps out at night when we're all sleeping and secretly washes his teeth."