Upvoted. It's not just you. "Pranking" someone while lying through your teeth is something I'd expect my 6y.o. to do, not grown ups.
It's like the show Punked, the best ones (thinking the kid from Malcolm in the Middle) relied entirely on the victim getting tunnel vision. If Franky had just been "yeah this is a prank" and it required someone to say "no, no its not" it kills the funny.
That was the main reason they stopped. There was a hidden camera show in the UK (all I remember is a guy with a huge phone shouting in awkward public places like a library) that the same happened. Their third season was in random places in Europe because they kept getting called out.
With prankees increasingly guarded, maybe there should be some leeway in this rule.
I'm assuming that the report of paranoia and the sentence "I was afraid that if I didn’t end the torture he might need psychiatric treatment" is comedic hyperbole, but I cease giving any "prank credit" after the roommate explicitly and correctly called the author out as the source of the ads.
>> I was afraid that if I didn’t end the torture he might need psychiatric treatment.
Better might've been to not flat-out deny it, but rather take his side in amazement and bewilderment, "OMG that is creepy", ignoring the accusation and then change the subject.