In the episodes filmed in Hawaii, Mike's hair becomes curly after the Bradys land in Hawaii. Reportedly, Robert Reed's hair became frizzy due to the humidity in Hawaii, and it was decided to keep it that way for the remainder of the series. However, in this episode, Mike's hair is straight.
When Peter is showing his volcano to Marcia and the other girls on the patio, it erupts and the lava flies all over the place and lands on the girls. However, even though Peter is standing quite close to the volcano, none of the splashing lava gets on him.
When Alice picks up the wires for the volcano, the exposed wires are wrapped around each other. The volcano should have been going off the entire time, instead of starting after she picked up the wire.