Which episode....

[Riahon]

had the mechanical Santa Claus??

[robyrob]

it was in the second season, episode #27- Guess Who's Coming to Christmas (aired 12/17/74)

Christmas episode where Fonzie has no place to celebrate the holiday.

A drawing of a snow-covered Cunningham house opens the show. Joanie asks if she can have some of the Chipmunks over, but Howard wants it to be a family-only Christmas eve. Chuck comes over to bring his laundry home and leaves a sweatsock on the Christmas tree. Richie, Chuck, and Howard go out to the driveway and try and fix the mechanical Santa Claus. In the next scene, Fonzie comes to Arnold's and brings everyone presents. Fonzie gives Marsha a locket that says "Your the ginchiest". Potsie tries to invite Fonzie over for a turkey dinner, but Fonzie is planning on a bus trip to visit family in Waukesha. Howard and his employees have a party at Cunningham Hardware. Howard and Richie have car problems and Fonzie fixes their car and turns down their invitation of coming over for the evening. As Richie goes back to the garage to give Fonzie his present (a 3 in 1 wrench), he sees Fonzie sitting alone eating a sandwich and ravioli out of a can. Howard and Chuck decorate the tree, and Richie mopes around thinking about Fonzie. Richie and Howard go over to Fonzie's apartment and try to convince him to come over to the house and fix the Santa. Fonzie is able to fix the Santa and then the Christmas tree lights which were not working. Fonzie misses his bus, pops some popcorn in the fireplace, and then reads "The Night Before Christmas". Richie takes a picture of Howard with Chuck and then Joanie and Fonzie look at a viewmaster. The family sits down and Fonzie says grace, "Hey God, thanks".

[dave insinga]

this particular episode was the best christmas episode from the whole series
had a true christmas feeling unlike some of the later ones