I always associated Counting Crows with Sheryl Crow, thinking it was a female group. Until I googled to see who the guys were that covered Big Yellow Taxi.
And my jaw just dropped.
I’m reanimating this zombie to add Bobby Caldwell. I’d always assumed that he was black.
Since this has been reanimated I’ll nominate Harvey Danger.
I only knew their song Flagpole Sitta from it being used as the theme to UK Sitcom Peep Show. One day I looked up the video on YouTube. The rest of the band look exactly like I imagined. The lead singer looks nothing like I imagined.
TCMF-2L
I first became aware of him on comedy channels on Sirius radio, so I always expected Jim Jefferies to look more like Paul Hogan than like Seth McFarlane.
Amy Winehouse should look like Aretha Franklin instead of a lot lizard from Des Moines.
Bob Segar. First time I heard him ( and heard OF him ) was in the mid-70s when the song ‘Night Moves’ was all over radio.
From his singing I pictured a muscular black guy with a shaved head. Was surprised to see a man who would look right at home as a member of ‘Black Sabbath’.
There is a discussion above about how tall Arnold Schwartzenegger really is. Look at The Ongoing Mystery of Arnold Schwarzenegger’s Actual Height | Mental Floss for more about this. Note that F.U.Shakespeare is quoted from an SDMB post. The link given there doesn’t work. It’s actually at Arnold Schwarzenegger is only 5''10? - #4 by F.U.Shakespeare
I found out how tall (short?) Ah-Nold was when he guest-hosted SNL during the “Hans & Franz” era. He’s in between Kevin Nealon and Dana Carvey, height-wise.
Has anyone mentioned Milli Vanilli - the public duo vs. the people who actually sang?
My surprise watching that was threefold: “Oh, I’ve heard that a lot and really liked it. Hey, wait, it’s in my iTunes ‘Real Deal’ playlist! Why did I never look into who did it?” then “He sure be white.” but mostly “Hey! He’s too young to be singing with all that soul. Yo, Markie Marc, go get a few decades of heartbreak and suffering, then you can sing and play like that.”
None of the guys of Greta Van Fleet look like they’re old enough to sound as much like Led Zeppelin as they do.
Highway Tune
Cool! Thanks for the notice Wendell!
A regular listener to the bugle podcast I was surprised when I watched Alice Frasers standup routine online. I did not at all have that mental picture of her in my head.
//i\\
He’s still way taller than Chuck Norris.
Yes, Boy George looked almost exactly the opposite of how I pictured him, back when I first heard ‘Do You Really Want To Hurt Me.’ In the post-punk era, it was difficult to be surprised by anything; but that was an exception.
Like an iceberg, most of Chuck Norris resides in another dimension.
I can’t believe you didn’t post any video links!
“What You Won’t Do For Love” is one of my favorite songs, and yeah, for decades, I thought that Caldwell was black. I finally saw that video a couple of years ago, and my mind was momentarily blown. 
Mike Geier, aka Puddles Pity Party is the poster boy for this thread.
Toni Watson, AKA “Tones and I”. Hubby and I had fallen in love with “Dance Monkey” and were going to look up any other stuff she’d done. Cue “NO. WAY.”
I tried posting one, and it somehow started playing a 1950s educational hygiene video.