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To continue from what Twentington said, Jack departed in early May due to his declining health, and a
USA Today article from July 27 indicates that no replacement had been chosen at that point. Based on the tapedate of the 1,000th nighttime show (August 17, 1988), which was the 25th show of Season 6, M.G. likely began on the daytime show around August 8.
I vaguely remember reading somewhere (I think it was an article) which noted that M.G. had left the radio station he was working at around late July;
Wheel was never mentioned, though.
Strangely, Kelly himself
claims on his official website to have done the show for two years, although anyone who saw Seasons 5-6 on GSN would know that wasn't the case by a longshot.
M.G. was replaced after the February 17, 1989 show, but as to
why...I have no idea, although it seems like a clear-cut "Oh, Charlie just became available!" (which I'm admittedly not entirely sold on, but hey). The recording date of Rolf Benirschke's first show (December 14, 1988) appears to suggest that Kelly was replaced during a Christmas/New Year's taping break.
I've also wondered why M.G. didn't do the Radio City Music Hall episodes in Fall 1988.
Most likely, it was either conflict regarding M.G. or the fact they're going on the road for the
second first time ever and wanted to hit it off big. And hey, it got Don Pardo on a real game show for the first time in 13 years.
I've read that Charlie took over (or at least was asked to take over) but couldn't because of contractual obligations with Chuck Barris. Is this true?
Depends on where you read it. If this was in someone's bio or an interview, then yeah, it's got weight to it. If you read it on some other forum, then I'd take it with a grain of salt. I've known people in television to not take other gigs due to network contracts, but not with production companies.
I'm not sure where this came from, but at the very least there's precedent -- according to
Randy West, when Charlie left
Wheel in 1980 (when Silverman canned the show and later reversed it) he became committed to the syndicated
Toni Tennille Show (a Hill-Eubanks series) and honored that commitment even after learning of the reversal; according to Randy, it was Charlie's credo that "A handshake is my word."
The timeframe for Charlie's return does match somewhat, as
The Dating Game and
The Newlywed Game ended in '89.
Because I've heard Pat Sajak say Kelly could not do the job very well.
For the record, I've never heard of this...or, for that matter, Pat giving
any sort of opinion on M.G.