Where is Goose, the Flerken with the bag-of-holding gullet originally from?
She is originally named Chewie in the comics.
In the MCU we don’t know, we have very little information on Goose and Flerkens in general. What we do know is that Wendy Lawson, aka Mar-Vell, had Goose with her. She seems to be somewhat knowledgable of the animal and knows more about her than the others, such as Goose taking to Carol.
Wendy Lawson: Goose likes you. She doesn't typically take to people.
Presumably then Mar-Vell brought Goose with her to Earth when she started working on the engine there. Before that though her origins are unclear and unexplained.
It is worth noting though that there has been interest to know more of the Flerken’s backstory and Kevin Feige has previously stated the potential of doing something for Disney+. So we may get an answer in the form of something on there at some point.
I’m wondering what has Goose been doing for the last 20 years? Can we get like a short film on Disney+ where we would like see that Goose was secretly offscreen at all of these important events?
I love it! And by the way, that’s one of the fun things about Disney+ is we could actually do ideas like that. The fun thing about introducing new characters and all these movies is suddenly going from a character that maybe you’d heard of if you’d read the books, but if you hadn’t, you’d never heard of him. And then you see the movie, you go, “I want to see more of that character.” And the fact that you and other people are asking, “When do we see more of the cat?” The question is “how long – what is the lifespan of a flerken?” It’s a good question.