Unexpected appearance of a banana in a chemical structure

This study introduces a banana into the diagram of a chemical structure:

“1,3-Bis(nitroimido)-1,2,3-triazolate Anion, the N-Nitroimide Moiety, and the Strategy of Alternating Positive and Negative Charges in the Design of Energetic Materials,” Thomas M. Klapötke, Christian Petermayer, Davin G. Piercey, and Jörg Stierstorfer, Journal of the American Chemical Society, epub November 28, 2012. The authors, at Ludwig-Maximilian University of Munich, Germany and at the University of Maryland, USA, offer this structural diagram:

(Thanks to investigator Mary Beckman for bringing this to our attention.)

BONUS (unrelated): Why a banana? Why a duck?