Re the thagomizer and the spiky end of a stegosaurus:
If that isn’t true, it should be! And if we all work at it, it will be…
A pet shop, with a large, well-fed boa on the floor. A parrot in a cage is saying
“Aaargh! Get it off me! … Pretty polly … Aaargh! Get it off me!”
One of the cows in a field looks up and says "Hey! this is grass! We’ve all been eating grass!
Regarding the Thagomizer, you might check these two references from Dinosaur National Monument and The Smithsonian Institution.
In fact, just by googling for “thagomizer” and “Thag Simmons” I found numerous claims on the Internet that the term is becoming more commonly accepted. I didn’t believe it, but it appears to be true. Weird. 
Pack of rapt dogs, staring upwards at a robed dog on a mountainside clutching a stone tablet inscribed, “SIT. STAY.”
(paraphrased)
“Professor Hendricks, having invented his dog language translator, tests it out”
The cartoon shows a man walking thru a neighborhood, and all the dogs are shouting “Hey!”
Out in the Old West, a prisoner has just broken out of the town jail, and is preparing to flee on a horse – who looks a little dazed. But the sheriff is standing nearby, amused, and says to the prisoner, “Nice try Bart, but that horse ain’t goin’ very far without THIS.”
And the sheriff is holding what appears to be the horse’s brain.
One year, my calendar had the aforementioned cartoon with the lady yelling at her dog. What we say to dogs: “Ginger! Stay out of the garbage! You’ve made a terrible mess! . . .” What they hear: “Ginger blah blah blah blah blah Ginger blah blah blah.”
It was followed the next day with a man yelling at a cat. "Fluffy, you must stop clawing at the drapes! I will not tolerate this behaviour any longer! . . . " What they hear: [A blank word balloon.]
Individually, amusing. Together, priceless.
One that hasn’t been mentioned yet:
Caption: “Video store in hell”
Scene: Video store racks filled with hundreds of copies of video tapes. All of them Ishtar.
One that hasn’t been mentioned yet:
Caption: “Video store in hell”
Scene: Video store racks filled with hundreds of copies of video tapes. All of them Ishtar.
Well, geez. Repetitive postings in hell?
“It’s Johnson. Just like all the others: all trussed up like a Christmas present with his hunting license stuffed into his mouth. I want this bear, Bob. I want him BAD.”
Trying to remember the exact wording of the dialogue here, but I’ll give it my best shot:
Two spiders are at the bottom of a playground slide. They have just constructed a web across the bottom of the slide. One says to the other, “If we pull this off, we’ll eat like kings.”
Love that.
“Let’s face it gentlemen - we’re not exactly rocket scientists”
The real reason for the extinction of the dinosaurs.
Flying saucers being piloted by dogs fill the sky; the suburban dog turns to his master and says: “So they’ve come at last. One thing before I go: roll over and play dead”.
This is a particular favourite of mine because I first came across it with a bunch of people I was studying Physics with at Uni. We were doing a piece of tutorial work on rocket propulsion at the time.
Also, there’s the one with Moses in front of a mirror, and the caption “Moses parts his hair”.
And the one guy poking around inside an enormous warhead, and his colleague, both with “Bomb disposal” on their jackets. His colleague’s saying to a nearby police officer “well, it’s an unusual bomb with a hair-trigger mechanism, and Bob’s wife left him last night so you KNOW his mind’s not on this…”
Just about all of them are good, but there’s one I never got. A sea captain is walking down a street at night and IIRC a large wave is coming around the street corner. The caption goes something like, “Captain <whathisname> was killed by a following sea” 
a following sea is a nautical term
FOLLOWING SEA - An overtaking sea that comes from astern.
In the Larson cartoon the captain is being followed by a sea, which presumably attacks and kills him. Nothing too complicated going on in this one (unless I missed the point entirely).
Am I to assume that a “overtaking sea” implies a wave breaking over the stern of the boat? Us landlubbers just don’t follow the lingo…
Add me to the list of “Cat Fud” as being one of my definite favorites!
Couple of others I enjoyed (heavily paraphrased, it’s been YEARS since I’ve seen these):
Ariline pilots in the cock-pit in mid-flight. One of the pilots is frantically shouting to the other, “Bob, the FUEL LIGHT IS ON! OH MY GOD, the FUEL Light is ON, we’re all GOING TO DIE! . . . oh, wait, that’s the intercom light.”
From inside the farmers house you can see out the window a cow sitting comfortably on the wire fencing, saying proudly and confidently to the other cows (who are looking on with much interest), “see, I told you it wasn’t electric” – but towards side of the frame is the farmer looking out the window with one hand on the power switch, ready to activate the fence.
… also vaguely recall some dogs in a parking lot (or street), one of them shouting, “all right! Rusty’s in the club!” apparently after Rusty had chased a car, or had darted through traffic… so many good ones…
There are so many…
One of my absolute favorites doesn’t even have a caption: the Antarctic, an ice plain, glaciers in the background, a very puzzled-looking penguin flat on his ass, and a solitary banana peel.
Also: The sun can be seen rising through the kitchen window. A small dachshund-looking thing is standing on a stool in order to reach the espresso machine on the kitchen counter. “While their owners sleep, nervous little dogs prepare for their day.”
Also: “Failed marketing ploys” and the “I cuss, you cuss, we all cuss for asparagus” van with smiling asparagus on top.
And: A group of birds are sitting on rocks protruding from a lake. The leader of the flock is instructing the others: “OK, everyone, we’ll be departing for Antarctica in about 15 minutes. … If anyone thinks he may be in the wrong migration, let us know now.” In the center of the flock, a single bird is wearing sunglasses and a flower shirt.
And: Daffy’s résumé. “Experience: Aug '63-Nov '67: Jumped around a lot and went ‘Woohoo, woohoo woohoo!’ Jan. 68-Sept.'83: Jumped around a lot and went ‘Woohoo, woohoo, woohoo!’…”
I particularly like the one with a group of students coming out of a Karate Dojo to see an alien saucer landed in the street with aliens pouring out; aliens whose bodies consisted of small brick walls and their appendages of boards. The caption read something like: “The students took the opportunity to practice their skills and save the town at the same time.”
They actually had this posted at an old martial arts school of mine.
THe institute for the study of migraines next door to the marching band school
“The dam bursts”
What we name our pets vs. what they name themselves.
(I am sheba, stainer of persian rugs)
Mohammed and the mountain.
The airplane with the “wings stay on/wings fall off” switch next to the recline button
“It was fifi, tragically, who was to bear the brunt of their aggression”
