Sidney Porter (O. Henry) was a contemporary of Samuel Clemens (Mark Twain). They died the same year; Porter attended Clemens' funeral a few months before his own death.
Was Porter referring to Twain's character Tom Sawyer or to Twain himself in the passage bolded below (rectangled in the image)? Sawyer (and Clemens himself) had curly hair and both were also known for "skipping school."
From "The Gift of the Magi" by O. Henry
When Della reached home her intoxication gave way a little to prudence and reason. She got out her curling irons and lighted the gas and went to work repairing the ravages made by generosity added to love. Which is always a tremendous task, dear friends—a mammoth task.
Within forty minutes her head was covered with tiny, close-lying curls that made her look wonderfully like a truant schoolboy. She looked at her reflection...
I assume also that the use of extravagant slang in O. Henry's By Courier (1906) was influenced by Twain's "Roughing It" (Buck Fanshaw / Scotty Briggs episode).
