The improv actually shows higher intelligence than just mimicry. So when he stumbled, he paused and sort of played mash up while stoll hitting the melody sometomes!
Have you tried, teaching him food related words? I have a couple that I could think of sticky bun, cinnamon roll, spice sausage. Let me know what you guys think of it.
Parrots naturally need to be in constant communication with each other in the wild. Although Apollo is not wild, he still has that instinct. He just knows a lot more words due to being raised by people, and he knows they generally respond to those specific sounds, so it prompts him to continue talking to get a reaction.
I don't know about the rest, but I can tell you it isn't an old channel. The videos might be from years ago, but the first video upload date for this channel is from 4 days ago.