Used in threads specifically devoted to puns. Here, people puntificate all through the week. Sometimes used by returning patrons who have been away for some time, announcing their re-appearance. People sometimes post pure works of fiction in Callahan's, and this keyword can be used to label them. Used to label an elaborate pun or shaggy dog story, which usually rambles on a bit before delivering the pun-chline.
Favorite books Note that the last example uses no keyword.
And in many cases, they won't. So, if a thread of conversation mutates severely, the subject line should change too. That'll help people a lot if they're trying to filter by keyword. You're also welcome to try a keyword not mentioned here, if none of the keywords mentioned above apply. Successful keywords tend to define a clear category, which won't be likely to change over the normal course of a discussion thread.