Wow, that's a difficult one. I've been serching for some information about this cartoon and it is very hidden. First I must notice that this is from the first Casper Series from the 50s. Casper appeared in children books in late 30s by his creators, Seymour Reit and Joe Oriolo (the first story was published in 1939) and then a short run of cartoons was released in the 40s.
The complete list of episodes from the second series in the 60s doesn't present this episode, therefore this must be from that first series. And that's all the information I have about it.
What I can analyze from the begging is that it has a very interesting meta-language and a cool interaction between comics and cartoons. All characters appear in their own comic-strip in a magazine that the boy who is asleep at the begging was reading. And "comics" characters run from one strip to the other.
Well, to much said. Enjoy the video!
Casper the friendly ghost-the missing shadow