Don Camillo's casual mention that he made a list of Peppone's secret arsenal before setting it on fire, also telling him he took a submachine gun for himself.
The submachine gun is a literal Chekhov's Gun: when Peppone and his men tell him they'll use all the ten millions they stole from the Germans for the people (meaning to build the House of the People), and if anyone protests they know how to deal with them, don Camillo replies with a casual "Me too" and pulls the submachine gun on them, before getting them to agree that three millions will be used for the garden city (to be used by the children of the people).
During the strike, the Communist picket farms, armed with rifles, shotguns and even submachine gun, to prevent strikebreakers from trying to work, which results, among other things, in some cows starving, with one being about to give birth to a calf. The calf being the last straw, Camillo grabs his rifle and sneaks into the stables to help the cows.
Peppone catches him in the act. Does he stop him? No: he helps. And he started the strike.
During the strike the communists had asked for reinforcements from the city, but they only arrived when the strike had ended. Having nothing to do, the comrades decide to get a drink in the town's pub and then provoke don Camillo... Who reacts by grabbing a 200 kilos table and throwing it on them before attacking. A Gilligan Cut later, Peppone and his friends are half-complaining/half-bragging to the bishop that don Camillo beat them all up, knocking out fifteen of them. Alone.
One for the bishop and his guile: after Peppone's complaint, he summoned don Camillo (who had no bruise or trouble to walk) believing he had organized an ambush, and upon hearing his version he made him prove it with his own (equally large) table... And then used the results to make himself pass for a strongman to his guys.
When the old town's schoolmarm dies, she asks to have the monarchist flag on her casket. As the king has literally just been exiled, Peppone's allies from other parties in the town council object. Don Camillo, who is there, seems about to explode, but first lets Peppone talk, and we get this gem:
Peppone*calmly*: "As the mayor, I can't help but recognize your decision. But as in this town it's not the mayor who's in charge but the Communists, as leader of the Communists I'll tell you that I don't give a damn about your opinion. Mrs. Cristina shall go to the graveyard with the flag she wanted, because I respect more her dead than all of you alive. And if anyone objects, I'll make him fly out of the window! Does the curate have anything to say?"
Don Camillo: "Finish your business here and now! You want to fight?! Then fight it out once and for all!"
The day of the opening of the house of the people and the garden city Peppone decides to try and win one over Camillo by closing off the main road between Brescello and the city with a 'broken' truck, thus forcing the bishop to take the long route and arrive late and allowing him to open the house of the people first. The bishop being a Magnificent Bastard, he realizes Peppone's trying to get him to be late, so he leaves his car to offer some help, 'stumbles', and when Peppone instinctively grabs him he doesn't let go and walks the road to the garden city with Peppone on his arm and the comrades in tow. Then, after learning of the house of the people (with don Camillo having told nothing about it to his superior), decides to give the curate a lesson by visiting the house of the people with don Camillo in tow without opening the garden city first.
He then makes a short speech to the comrades from the city at the house of the people, and they can't help but cheer on him.
In one of the first book's stories, "The Meeting", someone from the Liberal Party comes to the town to make a speech. When he gets on stage, the square is packed with hostile people wearing red scarves, and Peppone gets sarcastic when he lets him have the floor. The speaker only shows courtesy and respect toward other people's opinions and manages to win the crowd's (and Peppone's) grudging respect. When someone throws a tomato at the man, Peppone instinctively offers his red scarf - the one he wore as a partisan - for the man to wipe his face with; the man recognises the gesture for what it means and refuses, saying a plain old handkerchief will be better, and the whole town applauds both.