The party just cornered a random shopkeeper and you need a whole person in four seconds. Name, quirk, secret, voice — dealt.
Improvised NPCs die because they're only a name. The fix is mechanical: a quirk players notice immediately, a secret the GM knows and the players don't, and a voice note so the character sounds different from the last one. That's the entire load-bearing structure of a memorable NPC — everything else can be invented if the party keeps talking to them. Each card here carries all four elements so nothing is left to panic. Need a specific flavor of person? Set the role dropdown — merchant, guard, noble, clergy, criminal — and the job and secret bend to fit.
You never have to use the secret. But when a throwaway shopkeeper turns out to be reading the party's letters, your players will retroactively decide you planned them from the start. Improvised NPCs with secrets are how prep-light GMs get a reputation for deep plotting — take the credit.