Stolen from today’s Los Angeles Times Online Crossword but you can get yours from anywhere, once you answer this one:
What do these entities have in common:
Cheshire Cat
Alfred E Neuman
The Joker
Mona Lisa
The puzzle was fun in addition to this riddle, so there’s that…
Let me think…
Reminds me of that Charlie Chaplin song…
What do these entities have in common:
Dorothy Gale
Kermit the Frog
Rev. Jesse Jackson
Johnny Cash
You get to pick a group, if you wish…
I’m guessing rainbows, in spite of being unable to cite the Cash reference.
In what way are rainbows associated with Kermit the Frog and Rev. Jesse Jackson? 
The first Muppet movie starts and ends with Kermit singing The Rainbow Connection.
Rev. Jesse Jackson was associated with the Rainbow Coalition.
Well, thanks.
Duh! (Thanks)
While we’re in a silly area:
Alexander The Great
Kermit The Frog
Smokey The Bear
Attila The Hun
The same middle name?
Stan Laurel
Karl Marx
Sonny Liston
Edgar Allan Poe
Ryan Gosling
Sandra Bullock
Jack Chick
Samuel Colt
little critters?
For the OP is it they all have a unibrow?
See Post #2, please.
Good group. I’m stumped so far. Can you add one more to the group, maybe?
People featured on the cover of Sgt. Pepper’s Lonely Hearts Club Band
Next:
Bed
Pin
Ship
Corporation
Hospital?
Not what I had in mind.