Uncle Jay had a very annoying habit, as far as his wife, Aunt Marge, was concerned. Whenever he was on the phone or ran into someone he knew, he'd say, "How's tricks?" It wasn't just that the expression probably dated back to Julius Caesar; it was wrong. Grammatically.
"You cannot say, 'How is tricks?'" Aunt Marge would say. "You must say, 'How are tricks?'"
Of course, that ruined the expression entirely. People would look confused when they heard it. Since Aunt Marge didn't want to explain, she'd say, "I meant, 'Tricks is fine with me. How is they with you?'"
One day as she and Uncle Jay were strolling on Main Street, a man coming towards them stopped and cried, "Jay! I'm Cal, from high school! How's tricks?"
Aunt Marge put her hand on Uncle Jay's arm to stop him from answering and said, "Why tricks is just fine! How is tricks with you?" Cal fired back, "They is fine with me, too!" After that, Aunt Marge refused to leave the house.
Remember: How's (how is) is for one thing or person. How are is for more than one
1) ("How's/How are) it going?" said Santa to the elves.
2) Another elf asked Santa, "(How's/How are) Donder and Blitzen? They didn't look well this morning."
2) How are (After Santa left, the elf told the others: "Just messing with him!")