Either Friday or Next Friday showed someone pooping in a neighbor’s lawn.
Since we’ve broadened things,
American wedding - Stifler rummages through and eats dog poo.
While I have never seen the movie, you can see, if you really want to, R. Lee Ermey take a dump in the movie Saving Silverman.
Ir itmight have been Panic Room, where Jodie Foster did the same thing,
In Doc Hollywood, Michael J. Fox and Julie Warner are wandering around the woods when Warner suddenly “drops trou” and squats in order to contaminate the area around a deer-hunter’s treehouse or whatever to scare off deer who detect the human urine.
Bah, all these examples are merely poop simulations.
In Kings of the Road (probably the best movie Wim Wenders ever made), we actually see actor Rüdiger Vogler take a literal dump out in the desert. Graphic but tasteful (meaning filmed in a simple matter-of-fact way instead of for comedic or sensationalistic effect) and done in one long, single take.
You just answered the question I was going to ask, but I’ll take it further–are there any other movies (especially mainstream ones) where we actually see one of the characters pooping? Not that I’m interested in watching or anything, but it always struck me as the last taboo–we’ve seen people vomit, pee, spit blood, blow their noses, and have various kinds of sex, but showing somebody taking a crap is forbidden.
Doesn’t Steve Stifler eat a dog turd in American Wedding (American Pie III)?
E3
One of the characters in Shaft, the bad guy I think, is sitting on the toilet at one point and you hear the ‘plop’ sound.
There’s lots o’ dino crap in Jurassic Park and sequils.
The movie The Road To Wellville was all about evacuation - brought on by massive enemas.
In French Kiss, Meg Ryan’s character is enjoying a sumptuous breakfast of fresh fruit and assorted French cheeses on a train trio to Kevin Kline’s character’s home. She is wondering why she never does this in her everyday life.
Pretty soon she remembers exactly why: lactose intolerance.
That’s when she yells, “Man, you must have knocked something loose in there!”
That same movie features an Amish bowler played by Randy Quaid taking a dump in a urinal. That, my friends, is entertainment 
.
Along Came Poly had a great scene with Ben Stiller exploding on the toilet after an mid-eastern dinner. No door on the bathroom, just a curtain I believe, no TP, had to use a family heirloom bathroom towel to “cleanse” himself, then tried to flush it down the toilet and clogged it. All of this while his date is in the other room of a very small studio apartment.
Poop humor tears me up, almost to the point of embarassment. This one was a classic.
The movie “Jaaberwocky” has a scene of some guy (Michael Palin?) hanging his ass out the window of his house to take a dump.
Paul Giamatti Has a public toilet fixation, and a plot related poop scene in Confidence
There is a scene in Rob Roy where RR’s wife goes out for her morning tinkle by the lake.
In *Saving Silverman * there is a scene where the guys have convinced the Coach that he needs to do his business in the front yard because the bathroom is “broken”. I believe the phrase “pinching off loafs” was used, which I find incredibly funny for some reason.
Mr. Fishfinger was played by Warren Mitchell.
Incidentally, Mr. Mitchell played “Alf Garnett” in 'Til Death Do Us Part. This series was re-made in the U.S. as All In The Family.
What about John Travolta and bathrooms in Pulp Fiction?
How did we miss the famous scene in American Pie where guy who has sex with Stifler’s mom gets laxative slipped to him?
Robocop. While Bob Morton is in the bathroom mocking boss Dick Jones with a coworker, it turns out Jones was taking a crap and heard the whole conversation.