Bananas?

I brewed an Irish red back in May. I had one bottle left that wasn't quite a full bottle that had been in the fridge for a few months. The batch turned out great and I really enjoyed this beer. I hadn't opened this bottle just because it wasn't a full bottle. I poured it the other day expecting one of those great Irish reds I had enjoyed from this batch. I was greeted, however, with a very strange banana esque flavor. I know I've read that yeast can produce these flavors when fermented out of temperature range, etc. but this was the only bottle that had any weird flavors. Was it the fact that the bottle wasn't completely filled? I was just a little puzzled by this since the others were great.
What say you???

How was the carbonation? Any gushing or other unusual aspects?

All of the other bottles were just fine. This one...well, it sounded a little different i thought just because it wasnt a full bottle. but wasnt over carbonated or anything. poured normal.

Banana taste is a very common ester produced by fermenting too high and stressing the yeast. It's a very desireable off-flavor in Hefewiezens and Dunkelweizens, but Irish Reds, not so much.

Maybe that one bottle carbed at a higher temp than the others, or somehow experienced a temp swing that the others did not? Something like that...