Brominous Quicksilver is a state employed chemist, examining the dirt near the Everfree forest for signs of change. As such, he rents a room in the townhouse that the Apple family decided to build to support their income.
A few years back, a drug swept across Equestria. But rather than inducing a high to the user, it causes them to forget a memory of their choice. The abuse that ensues has infuriated Brominous to the point that he decided to take the job opening near Ponyville in an attempt to escape the influence of the drug that was so oft used around him.