The frequency illusion, also known as the Baader-Meinhof phenomenon or the recency illusion, happens when you learn about something for the first time (for example, a song or a fashion trend), and suddenly start to see it everywhere.
You might see it so often that you start to wonder if there is some sort of conspiracy! Fortunately, even if this illusion might make you question your sanity, there is a simple explanation. The song or fashion trend has always been there--you just were not aware of it before. You only notice it once you know about it.