"The Laughter of the Saints"
by F. Drouet, C.M. can be found here.

It has, of course, several mentions of St. Philip, including this one:

"In this gallery of cheerful Saints, a particularly honorable mention is due to St. Philip Neri, whom Goethe justly calls the 'humoristic Saint.' He was fond of playing...tricks on his novices, and if he saw one of them a bit proud of his new habit, he would send him out on some errand, with a ridiculous appendage, like, for instance, a fox tail, hanging over his back. The following anecdote, the authenticity of which is guaranteed by the best authorities, will suffice to illustrate this amusing feature of his character. One day he was sent by the Pope himself to some neighboring convent to inquire into the life of a nun who had the reputation of a Saint. The weather was horrible, and when Philip dismounted he was bespattered with mud from head to foot. The good Sister was brought before him, and judging at a glance that her air of compunction was rather overdone, Philip said abruptly while stretching out his leg: 'Pull off my boots, won't you?' The would‑be Saint assumed at once an air of offended dignity, and without any further inquiry the Pope's envoy put on his hat, went straight to his master, and told him that a religious so devoid of humility had no claim whatever to the saints' aureole. "