In this eposide Robert Reed's hair is straight. Even after the Hawaii episodes when his hair turns curly.
Greg announces on the first day of school that there are 111 days until Christmas vacation. It's not given when the vacation starts. 111 days before Christmas itself is September 5.
Alice: If they get any more mud on the patio, I'm gonna kill 'em.
Peter: (repeatedly) When I connect these two wires, little puffs of smoke will come up, and lava will come oozing out all over the volcano.
Mike: Marcia, there's an old saying: You can't take a step forward with two feet still on the ground.
This is an important milestone in the series as Marcia now enters high school.
This episode contains perhaps the best known subplot of the series, when Peter builds a volcano.
I seem to remember when Marcia is wearing her SCUBA outfit, Alice comments "You wouldn't get me into one of those things, even if you promised me mouth-to-mouth resuscitation with Cary Grant".