If you're wondering why the phrase "a owl"[sic] has been trending, look no further.
The phrase "A owl" is from a scene in the UK sitcom PhoneShop, in which two characters discuss an unexpected-- and possibly evil-- tattoo discovered during a date.
The owl joke is so popular, it has its own Facebook page.
However, those who didn't get the reference went straight into internet-pedant mode, and busted out the Twitter grammar-correction pens.
Note to internet pedants: everybody knows that your grammar correction is more about you than the grammar, but we'll leave that aside for another day.
... A owl?