I have that Alephbet telethon video on my shelf, I haven't touched it in years, but the big one that I remember they used (and dubbed over) was the Bert and Ernie sketch where Ernie says he wrote a short story, and he reads it to Bert, and, to Bert's disappointment, it's just the alphabet. Ernie doesn't finish it because he doesn't want to spoil the ending, so Bert won't read it on his own. The reading of the alphabet was obviously dubbed over to be the hebrew alephbet, and I think one of Bert's lines was also dubbed over, inexplicably (but, then again, I don't remember how the original version of the sketch sounds).
If I recall correctly, pretty much all of the dubbing didn't sound a whole lot like the real voices, and since only parts of the dialogue was dubbed over, it all sounded pretty jarring.