Alerts issued by the President
Alerts involving imminent threats to safety or life
Amber Alerts
What could possibly be so all-fired important that the president demands we give him our involuntary attention?
It's like something out of an old 1950s-1960s Sci-Fi movie, or episode of Star Trek, where the "Ruler" of some alien civilization summons his subjects by way of a siren. The film The Time Machine immediately comes to mind. Also, several episodes of the original Star Trek.
"Who is Vaal?"
"Vaal is Vaal. He is – everything."
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And...
Star Trek: Return of the Archons ("It Is The Will Of Landru")
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Scene from The Time Machine (1960)