Most scene stealing very minor movie role

And not having Connery would likely have resulted in someone other than Patrick Stewart appearing in the Mel Brooks version.

Tom Waits in The Fisher King is another brilliant one-scene bit.

And he may not have been maste thespian, and his dialogue was all in voice-over, but Mikhail Gorbachev’s cameo as himself in Faraway, So Close! is lovely, and even more wistful with his recent passing.

Bruno Kirby as the world’s biggest Frank Sinatra fan.

Good call.

Lone Star. A great film full of terrific actors, but for me Frances McDormand takes the prize with her one short scene.

The first of character actor Frank Gerstle’s 200-plus credits was one scene in D.O.A. (1949) as the doctor who famously tells Frank Bigelow (Edmond O’Brien): “I don’t think you fully understand, Bigelow. You’ve been murdered.”

Laurence Harvey, John Cleese, Yul Brynner, Roman Polanski and Raquel Welch all have highly effective cameos in The Magic Christian (1969).

“Klaus Hergersheimer, G-Section, checking radiation shields” is the answer to a legendary piece of Bond trivia: who is the guy who unwittingly allows Bond entry to Prof. Metz’s secret lab so he can get hip to the evil plan in Diamonds are Forever (1972). Given that he is played by Ed Bishop - the head of S.H.A.D.O.! – that makes the security lapse all the more stunning.

IMO, Tina Turner as the Acid Queen in Tommy (1975) stole the show among numerous other one-scene players.

George Gaynes in Altered States (1980) as a doctor who looks at an x-ray of William Hurt and declares: “This guy’s a fucking gorilla.”

Dean Stockwell as Howard Hughes in Tucker: The Man and his Dream (1988) evoked charisma, paranoia and disconnected thinking in his brilliant (and under-heralded) one-scene cameo.

Alex Cox adapted Borges’ Death and Compass (1992) for the BBC before getting enough money to pad and release it as a justly neglected feature in 1996. Nevertheless, Cox himself contributes a movie-stealing, one-scene cameo as the blind “Commander Borges” meeting an untimely demise (Tarantino is another fan of the director cameo as excuse for gratuitous death scene; I thought he did his best acting ever in Django Unchained as he exploded).

Monstro the whale in Pinocchio (1940) may be speaking some kind of language, even if the audience can’t understand it. One of greatest movie-stealing performances of all time, imo.

Edie McClurg in Plains, Trains, and Automobiles takes the wind out of Steve Martin

If OP will allow a little flexibility, I submit Boba Fett in Empire Strikes Back. All his few scenes are in the Cloud City portion of the film and he barely says a thing. But you can bet your bottom dollar it was his action figure I was playing with the most in grade school.

My example is a little obscure, because it involves some movie history.

In the 1956 movie Julie, starring Doris Day, who plays Julie, in a film noir, that also may be the first “crazy stalker movie,” Day is a flight attendant. On a flight sequence, there is an hysterical passenger, who is uncredited, but totally steals the scene, and stays in your memory.

This actress is Mae Marsh. After Lillian Gish, she was the most bankable actresses of the early silent era, and the runaway star of Intolerance– so much that her story was rereleased separate from Intolerance as The Mother and the Law. She was earning $2500 a week-- beginning in 1916.

Marsh officially left acting at the end of the silent era, “To spend more time with her family” (maybe the only time that was true), but actually kept a foot in the water doing bit parts. She had a 2-line role in the failed Paramount production of Alice in Wonderland, where she was masked the whole time. After that, she took a series of uncredited (deliberately) roles that were one scene, with a few lines-- or occasionally none at all-- she is the matron of the women’s prison in The Searchers.

Throughout the 40s, 50s, and early 60s, she made 3 or 4 uncredited appearances a year. You have to wonder how stars back then approached appearing with a powerhouse like Marsh in a tiny role.

Marsh was trying not to be scene-stealing, but in this one role, in Julie, it just couldn’t be helped.

Oh, and almost forgot this-- there’s an hysterical passenger in Airplane that is a riff on her (parody? homage?)

IMHO, the most scene-stealing scene in a movie, ever, was actually orchestrated to be that way. In A League of Their Own, there is a scene where the ball goes over the fence, and a black woman (who has no lines) picks it up, and burns it back to Geena Davis, with deadly accuracy.

It’s brilliant. It says “You excluded us at your loss.” All in one ball throw.

This, to me, was a brilliant was to handle the “whites only” rule of the actual women’s baseball league the really existed at the time.

It would have been historically inaccurate to include black women in the real league, but dishonest to exclude them without comment. This, to me, seemed the perfect way to comment on the exclusion while remaining historically accurate.

That scene makes me cry. It may be the most significant scene in movie history where someone steal the scene with no lines.

Cripes, I’m getting tears just remembering it.

This reminded me of another entry for the OP: Barbara Billingsley’s “I speak Jive” scene from Airplane!

Yes, Julie is one of the primary films that Airplane! is parodying (along with Zero Hour). I recently watched Julie for the first time; not a great film, but I definitely noticed that it was one of the inspirations for Airplane!

That moment in A League of Their Own is a good choice as well; the recent Amazon Prime Video series adaptation took that idea and ran with it (the series essentially follows two storylines with two protagonists; one a white woman who participates in the league, the other a black woman excluded from the league who eventually finds her own path to playing ball).

Levon Helm in Shooter. It’s otherwise a tepid film (several of the actors seriously phone in their performances), but Helm is brilliant.

Cloris Leachman is in one scene in a very forgettable late 90s Meg Ryan movie–“Hanging Up” The plot centers around three sisters–Meg Ryan, Diane Keaton and Lisa Kudrow dealing with their relationship to each other and their alcoholic father (Walter Matthau) who raised them after their mom left. Leachman plays the mom. Meg Ryan goes to meet with her and the Leachman is awkward and in constant uncomfortable movement while Ryan tries to talk to her. Eventually it escalates to Ryan getting angry at the mom and asking her why she didn’t take her and her sisters when she left. The reveal is that Leachman didn’t want to leave her husband, she wanted to leave her kids. “Motherhood just didn’t ‘take.’” It’s a heartbreaking scene…only good scene in the movie.

Oscar the Grouch in The Muppets Take Manhattan.

I think also the marriage officiant in The Princess Bride.

Rowan Atkinson as the nervous Father in Four Weddings and a Funeral.

“In the name of The Father, The Son, and The Holy Goat”

I’ll always love “The Bear Man” in True Grit (the newer version).

I vaguely remember every preview of that movie had to include that clip.

Deadpool 2?