A frog in the throat of a frog dominates the discussion in this study:
“To have a frog in the throat: micro-CT imaging of anuran prey in Ceratophrys ornata (Anura: Ceratophryidae),” Thomas Kleinteich [pictured here], Salamandra, vol. 51, no. 2, June 30, 2015, pp. 209-211. The author, at Christian-Albrechts-Universität zu Kiel, Germany, reports:
“The specimen described herein is a 70 mm (snout–vent length) female Ceratophrys ornata housed in the herpetological collections of the Zoologisches Museum Hamburg, Germany.”
Here’s detail from the study:
BBC Earth has a nice report about the report, with the headline “The Pac-Man frog with a frog in its throat“.
BONUS (unrelated): “A frog in your throat or in your ear? Searching for the causes of poor singing,” Sean Michael Hutchins, and Isabelle Peretz, Journal of Experimental Psychology: General 141, no. 1 (2012): 76.
BONUS (mostly unrelated): Dead Duck Day at the Natural History Museum in Rotterdam.
BONUS (entirely unrelated): “Double-throat fixing type acute frog” Chinese patent #203741653, issued July 30, 2014.