Rei opening the refrigerator in one episode to find Professor Kenjiro's deserted body sitting inside, his face still wearing the Oh Crap! expression it last had, cradling a watermelon in his lap. She understandably freaks.
When the girls force their way down to see Rei, Kenjiro is unsurprised by their sudden appearance, in fact stating that he was expecting Akane sooner.
Rei's parakeet greeting her with "Good morning!" when it's not morning, and her trying to tell it that.
Kenjiro's bombastic greeting when Akane 'disturbs his work' in the first episode, her playing along, and them finally hugging while Momo wishes they didn't have to do this every day.
In Episode 3, when Wakaba is chasing Akane, the pair run past a teacher, who admonishes them for running in the corridors. The pair apologize, resume their chase at walking pace, and slowly speed back up again— only to double back when the teacher falls over and spills a box of stuff. They help him pick it up and carry it back to his classroom (Wakaba staring daggers at Akane the whole way), and the moment the teacher's back in his room, Wakaba starts chasing after Akane yet again. It's a lot funnier than it sounds.
From the same episode, Wakaba's letter of challenge is, on the outside, indistinguishable from a love letter.
Aoi: What a beautiful envelope. Momo: It's so... (sees "Letter of Challenge" on the back)...cute?
Towards the end of the episode, when Kenjiro randomly appears on top of Momo's head, Momo reacts to Wakaba's understandably shocked reaction to seeing a talking ferret with a casual "Don't mind him. He's our grandfather".