How I felt about it. Two Mules for Sister Sara is more or less a continuation of the "Man with No Name" Sergio Leone trilogy. Eastwood was seemingly stereotyped in this character, originally from the TV series "Rawhide," and on through such films as Hang 'Em High and High Plains Drifter. A different Don Siegel-directed film, Dirty Harry, would at least give Eastwood a new setting for his squinting tough guy routine.
But it has to be admitted that Eastwood is good at it. One even cheers him on in the rousing finale, which pits Mexico revolutionaries against a better armed French battalion. It's a slaughter on both sides, but Eastwood gets through unscathed, apparently fully healed from his recent serious shoulder injury.
Eastwood's take-what-I-want attitude within his peculiar but rigidly enforced honor code has its appeal, no doubt. His performance brings no real surprises. Even when he approaches a stick of dynamite with a burning fuse, he's not in a hurry. After all, it's only a prop.
MacLaine, who gets top billing, has the more difficult role. She is a nun, who is a revolutionary, and (spoiler alert) a prostitute (too late!). This character is not as inconsistent as it first appears. While posing as a nun, she sneaks drinks and smokes, and even curses when under pressure. Once she blows her own cover, she continues to show courage more appropriate for a woman of faith. And she admits at one point, "I wish I still had my crucifix with me."
Eastwood and MacLaine have surprising screen chemistry, partly because their characters complement the other's strengths and weaknesses. She speaks Spanish, he doesn't. She has (convenient) knowledge about the garrison that he lacks. He has experience as a soldier, and is good with a gun and dynamite. Both prefer to fight than flee. Still, after absconding with half the French treasury, you'd think that he'd buy her a horse to ride on. But when closing sight gags can coincide with "happy ending," truth be damned.
The score is provided by Ennio Morricone, who also composed the Leone/Eastwood trilogy, cementing the similar style between the films. The key difference, however, is that Leone's films were supported by a tighter story, rather than a series of linked vignettes featuring likable characters.