If you leash them up to go outside, they will get all tangled up because they each wanted to be on the opposite side of the hand you were holding their leash in, go figure.
If you are running late to go anywhere, they will puke, or poop, on the floor.
If you change their blankets and take your time to fold up nice fresh ones and put them down, they will dig at them and mess them all up, then puke on them.
If you've just finally fallen asleep after struggling to do so for hours, you will wake up moments later to, you guessed it, a dog puking.
If you try for once to take them on a long walk by yourself (it's hard because of the leash tangling remember), you will wear flip flops and the grass will be wet and the dogs don't like wet grass so you try to drag them up a wet, grassy hill, all while sliding up it looking ridiculous in your flip flops. You get to the top of the hill and decide to head home, and on the way your dog poops in the middle of the road.
If you try to take them on a walk with your dad, you will get to the bottom of a very large hill and the dogs will refuse to go on, literally sit down and not walk anymore, and you and your dad will have to carry them back up said large hill and all the way back home, while laughing hysterically at how ridiculous you look.
If you try for a second time to take them on a long walk by yourself, they will get to the middle of the road and not go any further because apparently the salt from the snow is hurting their cute little feet and you will have to turn around and try to carry them both, all while they are literally screeching because their feet hurt and you look like the worst dog mom in the world, when all you were trying to do was take them on a nice walk. Then they will come inside, and, yup, poop on the floor right in front of the door.
If you are wearing your cute new Toms with hearts on them for the second time, the dogs will poop on the floor, you will step in it, then you will accidentally clean your Toms with bleach cleaner, ruining your brand new Toms.
The one time you leave your favorite moccasins by the front door, your dogs who never ever chew on anything, will chew them to pieces while you're at work.
Most of these aren't exactly "Murphy's Law" things per se, but they all are things I never expected to happen haha. Dogs! Can't live with them, definitely can't live without them.