So Julie drops Wally for Wayne and flaunts him all over school so Wally tries to grow the mustache. In Eddie’s Sweater Wally goes to Cindy’s house all very innocently and Julie finds out. She lashes out at Wally having never seen the two together. So why does Julie act so meanly and Wally doesn’t, then takes Julie back at the end.

And, also, assuming Julie is also a senior, who did she go to the graduation party with? And after going to the trouble of growing a mustache for her, and getting back together with her, why would Wally then go to the party with Kathy (especially considering what a jerk Kathy's father is, and the fact that Julie's parents are bound to know Wally)? Could it be just because Cheryl Holdridge had so many character roles to play and was possibly unavailable?

Good point but I think they needed Wally to invite a new girl with a difficult father so he could throw Wally out the door without explanation. Mr. Foster knew Wally quite well as a very honest, safe boy.

He could have gone with Mary Ellen. We know from a previous episode her father's a jerk, too.

BTW I don't want to start a whole new thread, but Lumpy was in a very early role in a 1955 Father Knows Best. It was uncredited...Frank Bank had only a line or two. He was an unnamed high school freshman, which shows he was much older than his role on LITB (even taking into account being left back twice.)

I didn’t know Frank Bank made a “cameo” on FKB?

He actually looked like a high school freshman in 1955 (or 56, if it was later in the season). The FKB episode involved a boy who was homeless, and sponged off various families by helping with homework. Of course, he latched onto Bud and the Andersons. Early in the episode Bud was eating in the cafeteria, and the unnamed Frank Bank character was sitting next to him.

I really liked the early seasons of FKB and is that show on Netflix. I remember seeing it either on a retro station or Netflix. I remember seeing the beautiful Barbara Eden as a friend of Betty’s. Anyone else from FKB who became famous? How about Robert Vaughn.

Susan Oliver, Robert Reed, Dick York, Diana Millay, Rita Moreno. Barbara Eden's episode was from season 4, "The Rivals."

Robert Vaughn was in season 3, "Betty Goes Steady."