I used to have this roommate, and every morning at breakfast he said "Cheerio, mate".
That was many years ago in college. After college I joined the Central Intelligence Agency, for those not in-the-know, usually abbreviated as C.I.A..
I got my stripes fighting the Red's, but everything changed after 9/11. They moved me to the secret assassination division. So many dead, all to keep my nation safe.
On the day that I would retire from my thirty year long career with the agency (that's what we insiders call it), I was supervising a drone-mission over tribal Pakistan. The operators, code name "Cereal 1" and "Cereal 2" were running point on the mission, scouting the area till we knew if we had Jihadis in our scope, or a Pakistani petting zoo for toddlers. These locations have a similar layout.
My friend from college suddenly called, but damn it if I didn't have my phone on speaker. "Cheerio, mate". Cheerio, the god damn go-signal for Cereal 1 and 2. They lit up that Pakistani petting zoo for toddlers so fast you wouldn't believe. That's why the CIA now includes goats between the ages of 4-9 as enemy combatants.