Johnny biting into the mitsudango, not waiting to hear Chie's instructions about how to properly eat them, and spraying the contents all over Yosuke thanks to not biting into the snack with his molars. All of which a reference to Part 8: Jojolion.
Nanako treats washing the dishes very seriously, and washes them in a particular manner that would be considered unorthodox. In true Araki fashion, she finishes washing a plate by saying a catchphrase.
Johnny having no idea Saturday is a school day in Japan. Cue awkward moment when Nanako breaks it to him.
Yosuke screwing up and dropping his Kunai on himself as a result of trying to show off to the Shadows.
Chie kicking Yosuke in the nuts for accidentally peeping on her. This was a result of him trying to prevent Teddie from peeping on Chie, while Johnny just watches and doesn't lift a finger to help until after Yosuke's kicked in the nuts.
Johnny screwing up with eating rice while using chopsticks. He eventually gets so frustrated that he just uses a fork to eat.
ALL of Shadow Yukiko's hammy and over-eggagerated mood-swings.
Shadow Yukiko hitting on Chie. It raises a few... odd questions if the real Yukiko actually likes Chie as more than a friend.
Teddie channeling the great Joseph Joestar shouting "OH NOOO!" while being perfectly in character.