Most annoying guest actor?

[Executive]

I vote for Evie Juster. After listening to dozens of episodes of the series (some of which she was in), I figured out today that this must be the woman with the whiny, immature voice who played whiney, immature women in some episodes. I'll bet anything she was hired to play children (both male & female) in others. Juster talked like a jester, and just gets on my nerves. Yet the late Ms. Juster wasn't young. From looking around the Internet out of morbid curiosity, I found that she was already pushing 60 when CBS Radio Mystery Theater started.

I saw Evie's name in the episode guide of General Mills Adventure Theater too. (That was the late 1970s CBS Radio series hosted by Tom Bosley, then still playing Howard Cunningham in Happy Days).
Then again a lot of actors from one show turned up on on the other...

[Executive]

Actually there is one Mystery Theater guest star just as annoying as Evie Juster, and that's Mercedes McCambridge.

Mercedes had no real range as an actress, yet on The CBS Radio Mystery Theater her characters were often described as being "young", "thin", and "attractive". What?! Mercedes McCambridge? HELLO! :D Radio listeners weren't fooled because we know she was middle-aged, plump, and average looking. We couldn't accept her in those kinds of roles. The only reason she kept coming back was because she was close lifelong friends with Himan Brown, who launched her career 30+ years earlier on his Inner Sanctum anthology series.

At least in "General Laughter" (which is actually one of the most depressing and boring stories in the show's long history), Mercedes plays an actress attempting suicide. It's too bad her sleeping pills didn't work....

[Fizzlestix]

for me, the combination of Mercedes McCambridge
and Elspeth Eric is just awful. i can deal with most of
Eric's writing, but with McCambridge's over-dramatic
style and rustic vocal work, i cringe every time.

[CardsFan]

Whenever I heard Mercedes I can't help but think of her role as the voice of the demon in "The Exorcist". William Friedkin's description of her voice, on the DVD, is funny. But I actually like her in RMT, especially in Carmilla which might be my all time favorite episode.

[Executive]

for me, the combination of Mercedes McCambridge
and Elspeth Eric is just awful.
I agree.

Before she became a writer, Elspeth Eric used to be a character actress in 1950s radio anthology shows such as SUSPENSE and ESCAPE.

[Executive]

On the opposite end of the spectrum, Morgan Fairchild was too good-looking for radio....yet at that time she was known from the CBS TV daytime drama Search for Tomorrow. (I don't watch those).

In 1976 Morgan did have the leading guest role in the CBSRMT episode "The Infernal Triangle", and I always though she was an OK actress. Even though she didn't really get into acting until around 1973, at the age of 17 in 1967 she was actually Faye Dunaway's double in the hit movie "Bonnie and Clyde"!

[Charlie]

I guess the most annoying to me would be Casey Kasem but I am sure I am in the minority there.

Charlie