The originator of the Mickey Finn fly color pattern and when it was first tied is unknown. The pattern became well known and popular when John Alden Knight of Williamsport, PA wrote about it in the early 1930's. Early in it's history it was called The Assassin. The final name Mickey Finn is believed to be a tribute to the actor Rudolph Valentino who died in the mid 1930's from a drug overdose (he was slipped a "Mickey Finn" as the term went back then).

Today, the pattern remains very popular and effective in freshwater and now has proven itself as a good saltwater color scheme. It is effective day or night on striped bass, weakfish (sea trout), drum (red fish), snook and bluefish.