So they had frogs and buckets in that galaxy but not barrels and fish? (Quotent Quotables)

This picture is from an actual article entitled "Frogs Can Help Make Milk
Stay Fresh Longer."  Here is the text of that article:
There used to be an old Russian wive's tale that if a
 frog jumped in your bucket of milk, it wouldn't go sour.
 As it turns out, that might be true because
 the peptides in frog's skin secretions are antibiotic.
 It also means that as more diseases become
 antibiotic resistant,
we might start turning to frog ooze to prevent infections.

Often in scifi and fantasy you'll see the author reminding you Hey this isn't your world it's a different one look how different they are tho like in this passage from Chuck Wendig's Star Wars: Aftermath: Life Debt: Superfluous Titles in which an alien bounty hunter is reflecting on how their attempt to free Kashyyyk*

The Empire— if those ships above even claim to be that, anymore— is now attempting to bomb this planet to oblivion. Already she knows how this will go: Many of the newly freed Wookiees are only peripherally free. Most are still trapped in settlements. Which means killing them will be as easy as firing a blaster into a bucket of frogs.

"Hmmm. Hmmm. Need a simile for something that's really easy to do. Something where the thing you're going after is just trapped there. Can't get out. Not fish in a barrel that's too quotidian. This is an alien planet. A long time ago. A galaxy far far away. Need to make sure they remember that. We're not down at the docks in San Diego here after all.  Nobody is shooting fish in a barrel. Who shoots fish anyway? Why is that the expression? And did they ever keep fish in a barrel?** I bet they didn't. No time to look it up now. Got to get this thing done. How about something more Star Warsy. Like blasters? Blasters are Star Wars. Like firing a blaster into... what would you fire a blaster into in Star Wars? ... ... ... like firing a blaster into a cantina full of Hutts... no, no... like firing a blaster into a energy globe of Gungans... no, wait, the memo said absolutely nothing that would remind someone of the prequels..."

"Hey, Dad, want to see my bucket of frogs?"

*BINGO*

____________________

*I had to look it up to remember that it was spelled with three ys. You wouldn't want to make the Wookies angry by misspelling their home planet. When Wookies get angry...

**Nobody is apparently sure where the expression 'shooting fish in a barrel' comes from***, but what you should know is that it's not the bullet that gets them, it's the acoustics: when you fire a bullet into the water of a barrel the shock wave of sound kills the fish. 

***If you go look up fish in a barrel on Wiktionary you'll see that another phrase for something that's easy is "duck soup."  Most people who write about this stuff say that "duck soup" has no clear origin as an expression for something that's really easy to do. But one commenter that I found traced the expression to a belief that Inuit make 'duck soup' by putting an entire duck into boiling water, feathers and all, and hence duck soup is easy to make.