It was a typical day for Jeff Zebulon, who spent his time preparing packages, sending letters to distant places, addressing customer concerns, and dealing with the elderly patrons who frequented the post office. The elderly were often the kind of customers Jeff dreaded the most. Though he found their complaints and quirks frustrating, he endured them with a forced smile, all while silently resenting their verbal abuse.

One particular regular stood out - an old droid named Zul. Zul came in frequently to pick up packages, always throwing a fit over the identification requirements. No matter how many times Jeff explained that proper ID was mandatory, the cranky android would grumble and protest, acting as though it should be exempt from the rules. Yet, Jeff remained firm, enforcing the policy despite Zul's impatience and outbursts.

One day, as Jeff braced himself for yet another exhausting interaction, he noticed something unusual. Zul entered the post office as usual, presumably to pick up a package, but something was off. The droid, who always relied on a cane to move around, was walking smoothly - gracefully, even. Jeff immediately assumed Zul had received an upgrade.

As the android approached the front desk, Jeff greeted it as always. "Hello, welcome to the post office. How may I help you, Zul?"

"Just here to pick up my package, as always," came the reply - except the voice was different. It was smooth and youthful, a stark contrast to the usual hoarse, rusted tone Jeff had grown accustomed to.

Jeff narrowed his eyes but continued as usual. "Alright, let's see some ID."

"Certainly," the droid responded without hesitation, producing a space license.

Jeff's suspicion grew. Zul never willingly provided identification. The real Zul always complained about having to show it, insisting their frequent visits should be proof enough. Keeping his composure, Jeff glanced at the ID and asked, "Okay, what's your date of birth?"

With confidence, the droid responded, "September 3rd, 2045."

Jeff smirked. "Wrong. It's January 7th, 2100."

Without hesitation, he pressed the silent alarm under his desk. Instantly, the fake Zul began to morph, its metallic exterior melting away to reveal a grotesque, blob-like creature with rows of razor-sharp teeth and furious, glowing eyes.

Fortunately, the post office was prepared for such incidents. Protective shields sprang up around Jeff as hidden turrets emerged from the walls and ceiling. In an instant, a barrage of laser fire struck the creature, reducing it to a mess of sizzling, oozing slime.

As cleanup drones rolled in to dispose of the remains, Jeff calmly filled out an incident report, sealing a sample of the creature's remains to be sent to postal headquarters for analysis.

With everything back to normal, he returned to his station - only to see the real Zul hobbling through the door, cane in hand, scowling as usual.

Jeff sighed, shaking his head. Honestly, I'd rather deal with the blob than with old Zul.