1) Xzibit, the dude in the yo dawg meme, is a rapper and host of the TV show Pimp My Ride. In Pimp My Ride they take someone's crappy beat-up car and deck it out. They usually end up putting crazy shit inside the car, things that usually pertain the the person's interests, like fish tanks, keyboards, fireplaces, etc...
"Yo dawg, I heard you like fish so we put a fish tank in your car so you can feed you're fish while you drive" would actually probably be a line on the show. Someone came up with the concept, what if someone who likes cars brought their car to Pimp My Ride? Hence, "Yo dawg, I heard you like cars so we put a car in yo' car so you can drive while you drive"
2) What's not to get, it's a picture of a penguin. Penguins are kind of awkward animals and the text on the image macro points out some socially awkward situation.
3) It's from some amateur comic strip style drawing done on 4chan I think. The son does something strange and there's a funny drawing of a man saying "Son, I am disappoint". It's just meant to be funny engrish kind of thing.
4) See Awkward Penguin except put a smiling dog and inappropriate text for the image
