Wyatt Earp examined some buffalo hunters in a Dodge City bar where they passed out and determined they had been given a Mickey Finn. The marshal left Dodge City in 1879 and headed to Tombstone where he made his mark. The term "Mickey Finn" was named for Finn who opened a Chicago saloon in 1896, and started giving spiked drinks in 1898 close to twenty years after Earp left Dodge City.
When Dora finishes singing at the church you can see the boom mic shadow in the upper right. This happens about 12 minutes into the episode.