Mark Yurkiw provides us with info on the lyrics to the original theme from New Tom & Jerry/Grape Ape Show.

The original New Tom & Jerry/Grape Ape Show theme was the same melody that was heard at the top of the cartoons when they were later shown alongside the classic T&J cartoons in syndication, but the line "It's The Tom And Jerry Show" originally was "It's Tom & Jerry/Grape Ape Show." When Mumbly was added, they dubbed in a spoken voice after this line, saying "And Mumbly too!" I don't remember if there were any different lyrics, but there may well have been. Also, there was a spoken part before the instrumental break, and I don't remember the exact wording, but it was something like "Introducing that famous cat and mouse, Tom and Jerry, and (something something something) The Great Grape Ape!" Don't quote me on that, it's not verbatim. This, of course, was changed on the reruns.