Sheldon would not be familiar with Ubbi Dubbi. Amy would not be familiar with Klingon.
Back in the 1990s a co-worker of mine mentioned that he needed German for his chemistry Phd program.
Sheldon (at this point) absolutely knows Ubbi Dubbi. It would drive Sheldon crazy to not know after the Klingon/Ubbi Dubbi exchange, and as many online sites as there are explaining Ubbi Dubbi, he’d have learned it that evening. Amy probably learned Klingon to be closer to Sheldon. I’m not as confident as Amy/Klingon as I am Sheldon/Ubbi Dubbi, though.
It sounded like “schnert” was German for “purr,” and “kulu” was Chinese. Google has failed me. Are those right?