Eggplant Parmigiana... with PB?

So last night I made eggplant parmigiana (from scratch! For the first time! Go, me!) for dinner. Husband Guy took a big bite, then blurted out, "This tastes like peanut butter! Did you put PB in this?!" "Of course not!" I replied. HG just looked at me like he didn't know whether I was joking or not. THEN he looked at me like, Poor thing is crazy. She doesn't even know when she's cooked with PB anymore. So, I leaned over and took a bite of his slice... and it DID taste like PB! I still have no idea why, and it was just that one slice! Is that weird or what? (And, of course I ate the rest of that slice...)