Mister Rogers: "Can you say..?"

So over the last two weeks, I've been watching a Mister Rogers' Neighborhood marathon on twitch.tv. It's in its last few hours as I write this.

Near the end, I was poking around the Internet for Mister Rogers information, and it occurred to me that in the shows I had watched during the stream, he had never done the bit where he asked the viewers, "Can you say [word]? I knew you could."

I remember seeing him say that, back when I was young watching the show. I watched during the mid-to-late 70s, so at first I thought it was possible that he only did it for a few years (The show slowly evolved over the decades).

I looked around to see if there was a clip of Mister Rogers doing a 'Can you say..?' bit on Youtube or on the Internet, but I didn't find anything. However - according to websites such as TvTropes, Mister Rogers never did that bit. It was done in parodies and references to the show, but it was considered a 'Beam me up, Scotty' type phrase that wasn't in the actual show. (Almost. TvTropes dug up that he said something like it once or twice - but I remember him doing it on a regular basis.)