NOC, a white beluga whale who was kept at the U.S. National Marine Mammal Foundation in California for several decades, began to mimic the sounds of the divers and biologists around him, presumably because his standard repertoire of clicks and whistles wasn't getting him any closer to the bucket of shrimp and the Men's Health subscription he'd been asking about. He would repeat a handful of different words to try and get some kind of response out of the people holding him captive, but for years nobody seemed to notice. Finally, one of the divers mistook NOC repeating the word "out" for someone on the surface calling for him to get out of the water. Honestly, we feel the fact that the first recorded incident of a whale trying to speak English was of one telling a man to get the hell out of his water tank says pretty much all you need to know about our standing in the animal kingdom.
Current Biology / U.S. Navy
"Y'know what? Let the door hit your ass on the way out."
Sadly, the effort NOC made only recently came to light after researchers at the foundation examined several old tapes of his "speech" -- NOC himself died five years ago. He only struggled with English for a few short years before giving up and going back to speaking plain old whale, because he quite correctly assumed that unless he made Shamu noises, nobody gave a shit.