"came through on the other side like the faces on a bad coinage...."
See in text (Chapter 2 - The Shadow)
This simile conveys the idea that Mr. and Mrs. Darling have rehearsed and remembered the events of the night many times, and each time they seem to find more blame for themselves. It is likely an allusion to the adage that a “bad penny always turns up,” meaning mistakes return to haunt the people who make them.
See in text (Chapter 14 - The Pirate Ship)
This could be a playful allusion included to appeal to pirate and fictional pirate enthusiasts. In Robert Louis Stevenson’s pirate adventure novel, Treasure Island, one of the main characters, Long John Silver, sometimes goes by “Barbecue.”