Interesting history on the Micky Finn:
"The information provided on the Mickey Finn especially interested me because it had details I was not aware of on the origin of this fly. Part of the appeal of fly-tying is not only crafting your own flies for fishing but also the history of some of the fly patterns and how they came to be.
I always knew that the Mickey Finn fly, which is a streamer tied with a silver body and red and yellow bucktail for a wing, had a long and illustrious history. It is an old pattern but continues to be a favourite among trout and salmon anglers to this day. Its popularity is probably due to the fact that it catches fish, even if it doesn’t represent anything in nature.
In the stamp booklet it claims that the fly was first tied by a Quebec fly-tier, Charles Langevin, in the 19th century. First known as the Langevin its name was later changed to the Assassin. I knew about the Assassin fly and how it was popularized by outdoor writer John Alden Knight. Knight is famous for his development of the Solunar Tables, which outline the best times for hunting and fishing based on lunar cycles.
The effectiveness of the fly for catching trout prompted Greg Clark, well-known Canadian writer whose column ran in the Star Weekly for years, to proclaim, after being on a fishing trip with Knight, that the fly was as effective as a Mickey Finn. Now, at that time the Mickey Finn was a famous drink, developed in New Orleans in the 1920s, that was very potent because it contained narcotics of some sort. As the story goes, famed actor Rudolph Valentino died from drinking too many Mickey Finns while at a hotel in New York and the term, slipping someone a Mickey, comes from that event.
Greg Clark’s renaming of the fly as the Mickey Finn stuck and Knight continued to popularize the fly through his writings in the 1930s and 40s. Time hasn’t dimmed its effectiveness and it continues to be one of the most popular streamers for trout and salmon in North America. I like to use it for sea trout in the spring but I also use it, in larger sizes, for salmon in the fall."
Full article from http://www.capebretonpost.com/ (Don MacLean) FULL LINK