Imaizumi singing it himself in the bath during the stinger counts as well.
Kanzaki figuring out Onoda's name
Onoda: Is she a cop!?
Naruko asking Onoda if he's an otaku due to his glasses and large backpack. (which is a common stereotype) Cue the other otakus in the figurine store glaring at him at the background.
The omake ends with Imaizumi volunteered into a box for Kinjou's magic trick, and Kinjou pulling out two absurdly large scimitars to presumably cut him in half. The title of the next episode comes up just as Imaizumi screams, and it initially reads "Trembling Imaizumi" before Izumida's name comes in from the side and bumps Imaizumi's out to produce the correct title.
The omake reveals that Onoda and Imaizumi are watching a Love Hime movie together.
In a Callback to Episode 1, Onoda convinces an injured Tadokoro to sing 'Hime Hime' with him as they climb the hill. Both the faces of Tadokoro as he is forced to sing along, and the other racers as the pair pass them while badly singing, are priceless. This doubles as a moment of awesome.
The omake where Teshima and Aoyagi are in the convenience store. As Teshima grabs a riceball flavor that Aoyagi usually eatsI] (ume), Aoyagi, in his head, starts telling Junta that he wants the tuna mayo riceball and starts saying tuna mayo in his head like a mantra until his voice starts to deepen. Eventually, Teshima picks tuna mayo and the taciturn Aoyagi is pleased.
Episode 41 (Season 2 Episode 3)
In the omake, Fukutomi spins plates alone but as the maids open the door, Fukutomi gets shocked and the plates break. He yells "I...AM STRONG!" in the most inappropriate moment.
Episode 42 (Season 2 Episode 4)
Manami talking to Toudou with his mouth full of toothpaste. It grosses Toudou out and nags at him to flush his mouth since he was spitting everywhere.
Manami's face when he realizes that he can't ride free like he wants.
In the omake, Shinkai and Arakita ask Fukutomi what he's going to do for Toudou's birthday party. Cue in the previous episode's omake where he was spinning plates, and the usually stoic Fukutomi starts sweating and after getting pressured by his teammates, he stands up and yells, "IT'S A SECRET!"
Episode 43 (Season 2 Episode 5)
Onoda asking Midosuji if he liked anime due to his constant use of the word "zaku". (a Gundam term) Midosuji was thrown off since he did not expect Onoda to ask such a question.
The omake where all of Sohoku sings Love Hime, much to Makishima's horror. He claps a bit at the end.