Originally Posted by Sam Flynn
As Pooh-Bah says in The Mikado, "Merely corroborative detail, intended to give artistic verisimilitude to an otherwise bald and unconvincing narrative".
Exactly. There's a good take on this concept in a now defunct comedy show, in which the couple attempts to lie to their friends so as to get out of a party they do not wish to attend, and they make note of how a good lie should include otherwise bland or seemingly unrelated detail.
Everyone has done this to some extent or other when making an excuse.
Awh, I couldn't go in the end, I was a bit ill, been up all night coughing and sneezing. Woke up today and went to the doctors, I saw Bill on my way, but he didn't see me.