Although Blacky, Opie's imaginary black horse with the white spot on his nose is a little on the invisible side, an actual horse sticks his head through the Taylor's kitchen window in the original sponsor ad that ran during the broadcast. The Ad was for Jello Pudding. Most the original sponsor ads are bonus features on the Season 3 DVD.
While Andy is a wise father, this is one of those times that Opie's reasoning has proven his father wrong.
(Andy comes downstairs after talking with Opie about Mr. McBeevee)
Barney: What did you do?
Andy: I told him I believed him.
Barney: You told him you beli...? But, Andy, what he told you's impossible.
Andy: Well, a whole lot of times I've asked him to believe things that to his mind must have seemed just as impossible.
Barney: Oh, but, Andy... the silver hat, and the jinglin', and the smoke from the ears... what about all that?
Andy: Oh, I don't know, Barn. I guess it's a time like this when you're asked to believe something that just don't seem possible... that's the moment that decides whether you got faith in somebody or not.
Barney: Yeah, but how can you explain it all?
Andy: I can't.
Barney: But you do believe in Mr. McBeevee?
Andy: No... no... no. I believe in Opie.