puppy straddling its older friendNew puppy meeting her big sister. (Photo: DiggyPablo/Reddit)

When you decide to bring home a new puppy, you're obviously excited about the new addition. But the dog or cat that already lives in your home may not be.

"Though you and your family want your new puppy to be friends with your other family pets, you have to realize that your resident pets will not be wearing party hats when you walk through the door with a new companion in your arms," says dog trainer and behaviorist Sarah Hodgson, author of "Puppies for Dummies."

"Young puppies in particular are annoying to other animals — and the oodles of attention he’ll get will be off-putting to the resident pets. Some time must pass (up to six months in some cases) for everyone to get used to each other."

We've rounded up lots of images where the new puppy caused some consternation, curiosity and eventually friendship with the primary pets in these households.

cats spying on new puppy The cats are a little suspicious of the new four-legged stranger. (Photo: panda_nectar/Reddit)

In some cases the original pet just isn't so sure about the latest addition.

dog rolling eyes at new puppy The eye rolling is a dead giveaway. (Photo: HarroMongorian/Reddit)

Once in a while, there can be a bit of a standoff.

Cat on stairs, staring at puppy. When in doubt, go to higher ground. (Photo: Malachi_-_Constant/Reddit)

But eventually, love (or at least tolerance) will often prevail.

cat hugged by golden retriever puppy Is this cat happy about or just tolerating the new puppy? (Photo: bananawith3legs/Reddit)

Sometimes even the pups next door are curious about the new guy. (Can you see all three of them?)

Bassett hounds checking out new puppy The neighbors really want to meet new puppy, Mr. Flint Eastwoof. (Photo: Reddit)

But no matter how cute the new puppy is, once in a while, all you get is a scowl.

dog is scowling at family's new rescue Judy is scowling at her family's new rescue, Carl. (Photo: diamondbro43/Reddit)

Sometimes it works out great and there's an instant bond. In this case the older and wiser dog realizes it's her job to take care of the new pupper.

old German shepherd guarding new puppy This older German shepherd is guarding her new puppy friend at the park. (Photo: fallsforever/Reddit)

... but sometimes that protective instinct is missing. Like pouncing on the new pet's head from the couch when you thinks no one is looking.

cat watching new French bulldog puppy This Devon Rex cat doesn't like her new French bulldog sibling. (Photo: datman510/Reddit)

Those puppy teeth can be sharp, but patient, older dogs sometimes have a lot of tolerance.

dog wrestling with new puppy This little guy just showed up from the Humane Society. (Photo: foeva/Reddit)

And they'll even let the new guy have the best bed.

adult and puppy dobermans sleeping It's sleepy time for these big and little Dobermans. (Photo: trippyyy/Reddit)

Depending on a cat's personality, they might hide or they might let the puppy check out its new fluffy friend.

cat tolerates its new puppy This patient kitty is tolerating its new puppy ... for now. (Photo: cjnj/Reddit)

At the end of the day, it's all about a good hug.

older Lab hugging new puppy This older Lab is taking care of its new puppy. (Photo: Clurrrrrr/Reddit)

And who doesn't like to snuggle?

dog with new puppy friend Dog watches out for its napping new puppy friend. (Photo: Imgur)

So, just remember, for the original pet, it's a series of ups and downs. (He'll grow out of this stage, right?)

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.