The purpose of my post is not to take away from the images, but to point out that with deliberation and purposeful intent, it is easier to take this kind of photo than you might imagine.
here are some comments on photos where timing is NOT super-critical, but alertness to foreground juxtoposition is critical, and other related things, like planning, and background/foreground perspective manipulation.
6 horse took over. This is not so much timing as just being aware of juxtopositions. It's the same principle, in reverse, that the photographer uses on every shot where he chooses an angle to give a clean background, such as avoiding trees growing out of a person's head. In this reversed principle, we have a horse's head growing out of a person's body.
7 Cold inside: this is high speed flash. It's fairly easy to time this sort of shot. Freezing the action is what adds the interest. Timing is an element, but not as critical as you might imagine, particularly with you calling a countdown for the assistant with a bucket.
8 Puppy fishing: again, it is the justapositon in play that makes the visual pun. The action here would have been quite slow. The corresponding hair color between girl/dog and the fact that we see the girl's (dog's) snout in just the right position is what makes this shot so much fun.
9 Hat too small: If the train was stopped in the station, which appears to be the case, this is just juxtaposition, timing is not critical at all.
10. Caught in Surprize : This IS a great example of great timing. I would bet that the photographer shot thousands of similar photos before he got this timing shot.
11. Blowing fire: no special timing here, most likely. Shoot enough photos in this juxtaposition, and you WILL catch a tongue of flame "originating" from the dog's mouth.
13. Blow out: not hard at all. Give a countdown to when you open the bottle or insert the mentos1, shoot on burst mode with high speed flash. The soda pop explosion lasts several seconds.
15. Shadow couple: this is about planning and intention. The photographer chose a good background on a busy street, and just waited for passing people to happen to make the right shadow. That involves some timing, but on a busy street you could have hundreds of chances to get such a shot, particularly if the shot is staged using cooperative models.
I'll point out that this collection give NO credit to the photographers, and no links to their own web pages. It is likely copyright abuse, in my opinion.
I won't go on, except to encourage you to try to make your own "pseudo-timing" juxtapostion photos yourself sometime. Here's one of my own that doesn't seem so much like timing, but makes strong use of juxtaposition to compose the shot.
Of course, my avatar is not so much the result of perfect timing, but simply of posing inches behind a hummingbird feeder, and taking a photo each time a hummingbird comes to feed. After all, a hovering bird does not really move very fast, in comparison to when he's zipping around in fast forward mode. It just took planning, intent, persistence, and not-so-fast reflexes. Easy.