Under cross-examination from Borgesi lawyer Christopher Warren, Aponick maintained the money the government paid him never played a role in his decision to switch sides.
"You're making it sound like the two are inextractable," he said, "like George Borgesi got charged, so I got paid."
Instead, Aponick told jurors, the money went toward his housing, clothing, and relocation expenses as a protected informant and to pay for a necessary eye surgery.
"Now, I'm not a cross-eyed junkie fat rat anymore," he joked. "I'm just a rat now."
Prosecutors have called Aponick as a key witness in their case against Borgesi, who they say continued to oversee a profitable loan-sharking and bookmaking operation from behind bars.
He told jurors Wednesday that Borgesi often discussed his ongoing crimes and tried to recruit him to the Philadelphia mob.
He and Borgesi grew close during their time together, Aponick said - often joking, roughhousing, and trading war stories in their cell.
Early on in his cross-examination Thursday, Warren pressed Aponick to clarify that relationship, especially the prison cell wrestling bouts mentioned in previous testimony.
"What? Are you implying we're [gay] or something?" Aponick shot back. "I can say a lot of things about this guy - but he ain't [gay]."
But it was what happened after Aponick's release that consumed much of Warren's questioning Thursday. Two months after federal prosecutors lobbied to have him released early, Aponick returned to Brooklyn and launched into a bank robbery spree.
He told jurors he needed the money to pay off gambling debts owed to a rival mob family.
"I didn't want to break the deal," he said of his plea agreement Thursday. "But all [the FBI] could do was put me in jail. These other guys could hurt or kill me."
Infuriated, agents stopped taking his calls. But Aponick continued trying to work his way back into the government fold.
Only after an anonymous website posting identified him as an informant in 2005 did agents again make contact.
Though Aponick was placed in witness protection, prosecutors deemed him too problematic to call during their first trial last year against Borgesi and his uncle, reputed mob boss Joe Ligambi.
That jury deadlocked, prompting a reevaluation of Aponick's usefulness. But three months before he was scheduled to take the stand in the retrial, Aponick was arrested again - this time for allegedly shoving his wife out of a moving vehicle, a charge that was later dismissed.
Each time he screwed up, Aponick conceded Thursday, he hustled to earn back the FBI's trust.
"[I] could be back in business against ol' Georgie Boy," he wrote in one letter to agents. And this time, he added, "I'll work totally free of charge."
Aponick is expected to continue testifying as the trial resumes Friday.