A Finnish phrase: “toimii kuin junan vessa“, or “works like the toilet on a train”.
I have no idea where that comes from.
The only special insight I have about train toilets is from my year in the army; the army train had a tad primitive carriage whose use-instructions included not shitting when the train wasn’t moving. I gather under the lid there was a hole and nothing more, and the station people didn’t want our stink.
So, “works like a train toilet: only once you get it moving”. (“Well I admit pushing down skyscrapers’s a weirdish hobby, but it’s easy like a train toilet!”)
Or maybe it’s “works like a train toilet: like a terrifying gust of icy wind at your bare privates”. (“Whoa, you really scared me like a train toilet!”)
Maybe “works like a train toilet: all’s fine until there’s a sudden deceleration and then whoops you’re on the floor except it’s a wall and the toilet bowl’s on the other wall and there’s a brown fountain —” (“Then it turns out her sister’s the chick I accidentally choked to death in 2006. Things went downhill then. A real train toilet of a blind date.”)
Or how about “works like a train toilet: it’s the only choice, outside wrenching open a window and whizzing out.” (“Of course I apologized. When a naked biker with a sawed-off shotgun with a bayonet and a hard-on is staring at you, an apology’s pretty much the train toilet thing to do.” — “Wait, a shotgun with what?”)
Hmm. Or something “works like a train toilet: laxation without relaxation, because you’re so bloody afraid of missing your stop.” (“Bah! It’s a total train toilet job — one moment of carelessness and it all blows up in your face. And I always thought baking was nice and relaxing, but no — one moment of inattention and you’ve got a fucking Krakatoa on your hands! With a facehugger pie to show for all your work! Try to relax when it’s in the oven, burbling! And likely watching! What a monster have these hands wrought! What a monster!”)