Sherlock Holmes in Disguise

There's an old saying that you can't kid a kidder, but maybe that's not true. A young man named Barry Landers, giving a talk at the "Investigating Arthur Conan Doyle and Sherlock Holmes" colloquium in my novel No Police Like Holmes, makes an observation about Holmes and disguises.

Here's an excerpt, including a few sentences that only make sense in the context of the book:

“Sherlock Holmes is, to use an overused phrase, a ‘master of disguise,’ ” he said. “We’re not only told this in the canon, we’re shown it. At different times Holmes appears as a common loafer, a drunken groom, the Irish-American Altamont, the rakish young plumber Escott, a French workman, an Italian priest, a Non-conformist clergyman, Captain Basil, an opium smoker, the explorer Sigerson, an elderly bookseller, and an old woman.”

Disguise, yet. And Mac sat there, back at the front of the room now, hanging on every word as if he could disguise himself as, say, a “rakish young plumber.” Was he really on to something with whatever he had asked Decker or was it just B.S.? A toss-up. With Mac you could never tell. He was, after all, a professor.

“What is interesting to note,” Barry Landers went on as I inched my way toward the door, “is that Holmes himself is more than once fooled by disguise. In A Study in Scarlet, Jefferson Hope’s friend poses as an older woman, causing Holmes to say later, ‘We were old women to be taken in.’ And in another famous sex reversal, Irene Adler dresses as a man the evening she walks by Holmes in Baker Street and says, ‘Good-night, Mr. Sherlock Holmes.’ ”

What is your favorite Sherlock Holmes disguise? Are there any other instances of Holmes being fooled by someone else's disguise?