Many authors in the past have taken this idea (including John Green) of acting in films, but this is amazing! I was in my bedroom watching part of "The Wide Window" and I noticed something minor, but something BIG! Author Daniel Handler actually is in "A Series Of Unfortunate Events!". Take a look at this image I took.
Now this may appear to be just a normal actor, but don't let the disguise fool you! To confirm this find, I checked on the IMBD and found some very valuable information!
The link is here: http://www.imdb.com/title/tt4834206/
If you look down the page a little, it says Daniel Handler and it also says he played the role of "Fish Head Salesperson" in 3 episodes! Not one, but three!
Now, Lemony Snicket made himself unknown during the time that the books came out and fairly recently announced his real name. Now, if you notice in this interview, he looks almost identical!
So, yes! This brilliant author has appeared in this Netflix Original! Happy (or unhappy) watching!