“We can't take in every stray that comes along.”
Your kids found a homeless cat. They want to keep it. You're not going to let them keep it because you already have enough pets. You tell them this.
We can't take in every stray that comes along.
The phrase "take in ___" means to let a homeless animal live with you.
If you use words like "it" or "them" as the object, they will come between "take" and "in":
They wanted to take it in. I was like, "No way."
Sometimes people also use the phrase "take in ___" to talk about letting a person live in your home.
A "stray" is a pet which doesn't seem to have a home or master. Cats and dogs are most often called "strays".
You can call an animal "a stray" or you can say "a stray cat", "a stray dog", etc.
This is a phrase that you use when someone isn't very selective. In other words, if someone says "yes" to everything, even though it's a bad idea, use this phrase:
She'll sleep with any guy that comes along.
You're highly qualified, so it's not like you have to take every job offer that comes along.
In the example above, the speaker says that they can't take in every stray "that comes along". She means that they have to be more selective in deciding which animals to keep.