I have seen quite a few Koko cartoons and it's a darn shame that he's pretty much forgotten today. I am sure most of it is because he was mostly a silent film star...and very few people would even consider seeing any silent film...even a short one.
Koko was created by the Fleischer brothers--the same folks who later created the Popeye and Betty Boop cartoons. Using their own invention, the Rotoscope, Max Fleischer animated and appeared in the films while his brother, Dave, was the actor who acted out Koko's movements...and using that machine, Max traced over film footage of Dave to create these wonderful shorts.
In "Invisible Ink", Koko is his usual self...in other words, he's a bit of a jerk...but a likable jerk! It begins with Max trying to make a cartoon. And, like they did in the good old days, he's using an inkwell...but Koko is hiding inside and doesn't want to cooperate. Eventually, Max tries to trick Koko into coming out...and Koko then decides to use the same strategy to trick Max. It's all very clever and exactly the sort of wonderful combination of animation and real life footage that made the cartoons so popular back in the day.