In addition to English, Amy and Sheldon apparently have at least rudimentary skills in German, Mandarin, and Navajo. Sheldon and Amy could previously be seen making attempts at speaking German during their first 'Fun With Flags' webisode in The Beta Test Initiation (2012). Sheldon was learning to speak Mandarin (poorly) during The Tangerine Factor (2008), and later recognized the tattoo on Penny's buttocks as the Chinese symbol for "soup" in The Adhesive Duck Deficiency (2009), so he may have used his knowledge to translate 'Soft Kitty' into the language.
In addition to playing a floor harp, Amy apparently also has at least a rudimentary mastery of the zither, or auto-harp.
Penny used to stop for a 'bear claw' during her morning run The Cruciferous Vegetable Amplification (2010) but now she stops for a doughnut.
Title reference: Sheldon losing his memory.