xkcd #3232: Countdown Standard
Title text:
Anyone who is caught counting 'three ... two ... one ... zero ... GO!' will be punished with a lifetime of eating only ISO standard food samples.
Transcript:
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Source: https://xkcd.com/3232/
I just say "THREE!". It's the "ONE TWO THREE!" variant but I skip "ONE" and "TWO".
If you're not ready now, you won't be after the count down.