"Hey $hithead come here" is from The Jerk with Steve Martin.
He is awakened in the middle of the night by a dog barking and scratching on his motel room door. He assumes the dog is trying to tell him something and begins questioning the dog "is there a robber? ...a tornado?... a fire? -ruff ruff- A fire, oh my God we gotta warn everybody, I've read about dogs like you. You're a life saver, that's what I'm gonna call you Lifesaver." He then proceeds to wake the entire motel. As the sun is coming up, after the fire department tells everybody they can go back to their rooms and it was a false alarm, an elderly oriental guy walks up to Martin while he is holding the dog and says "Hey mister, don't name that dog Lifesaver. Call him $hit-Head!" "Yeah, $hithead, alright." So he names the dog $hithead.
The other scene you talk about sounds like Harold Ramis in Stripes. He is teaching ESL (English as a Second Language) to adult immigrants and asks if anybody speaks any English already, one of the students raises his hand and Ramis asks him how much he knows the guys says "Son of b!tch, $hit", no sooner than he says it the rest of the class (in unison mind you) says "Son of b!tch, $hit". Ramis goes on to teach them to do the 'doo ron ron ron, a doo ron ron' response to his "I met her on a Monday, and my heart stood still" prompt.
"I'd resent that if I were sober." Lt. Col Henry Blake
Both by adults in the movies I mentioned. I'm not sure of the exact lines, but if you're looking for and older movies (70's era) with precociously cussing kids and a curmudgeonly old guy teaching them more bad habits, I'd go with the Bad News Bears. The orginial of course with Walter Mattheau and Tatum Oneil.
"I'd resent that if I were sober." Lt. Col Henry Blake