It's a long way from Cocoa Beach to Dallas, but that's where Larry Hagman and Barbara Eden will reunite.

The former co-stars of the 1965-70 sitcom "I Dream of Jeannie" will be together again for the first time when Eden joins the "Dallas" cast for several episodes during the upcoming season. (There was a "Jeannie" reunion movie in 1985, but Wayne Rogers played the role of Tony Nelson.)On "Dallas," Eden will portray a woman attempting to buy Ewing Oil.

That would seem to rule out the possibility of Eden calling Hagman "Master."

And she won't be around long, but don't expect her to disappear in a puff of pink smoke.

***

CHER AND CHER ALIKE: The multimedia princess will also be making an appearance on CBS soon.

"Cher at the Mirage," a tape of the Academy Award-winning singer/actress' Las Vegas show, will appear on the network sometime during the 1990-91 season.

It will mark Cher's return to CBS after 13 years. The former star of "The Sonny and Cher Comedy Hour," "Cher" and "The Sonny and Cher Show" did a couple of specials for ABC and NBC in the late '70s but hasn't been back to the Big Eye since 1977.

***

SAME OLD TODAY: The changes NBC has made in its troubled "Today" show haven't helped much in the ratings, at least not yet.

The first week that Joe Garagiola and Faith Daniels joined the crew, the ratings were up ever so slightly. The second week, they dropped two-tenths of a point.

And more importantly, "Today" is still well behind first-place "Good Morning America," which has won the ratings war for 25 weeks in a row. The most recent numbers showed "GMA" with a 4 rating and "Today" with a 3.1. ("CBS This Morning" is a distant third at 2.1.)

Why does anyone care about this? Because "Today's" slide is costing NBC and its affiliates millions of dollars in advertising revenue.

***

BLAMING THE MESSENGER: Tom Capra, the executive producer of "Today," last week blamed much of the show's troubles over the past few months on the New York newspapers. "I think we have been treated shabbily," he said.

Geez, but it seems to me that the press in the Big Apple didn't make the decision to replace Jane Pauley with Deborah Norville . . . or make Bryant Gumble write that memo . . . or insist the Willard Scott be a buffoon . . .