Shout Out / Asobi Asobase

Manga

• The male student that gave the Student Council Vice-President her Gyaru Girl makeover wears an outfit and style similar to Giorno Giovanna.
• When Olivia asked her brother for advice to improve her English, he gave her a copy of Sesame Street. However, this is seemingly all for naught, as Olivia only remembers Cookie Monster's lines. This triggers a callback to Chapter 39/Episode 11 after Sainan-sensei goes into another zombified frenzy over the sight of a cookie Olivia was holding. The narration even called him the true Cookie Monster as such.
• The funky hairstyle Olivia gives Kasumi in Chapter 43/the OVA is a dead ringer to Yugi Muto. To further drive the point home, Hanako snaps that only people who are obsessed with Shadow Games have the hairstyle (in the anime, she instead complains that she looks as if she's about to join an underworld card game using her split personality).
• Oka whips out a "Love Note" as she goes to Kasumi for advices in Chapter 54, complete with black cover and eerily-similar font type.
• The splash page for Chapter 54 has Olivia and Hanako dress up as Holmes and Watson, respectively.
• Chapter 71's title page has Hanako lament she can't do a "Bigger on the Inside" joke with a glass wall telephone booth.

Anime

Episode 1

• Hanako rather suspiciously denies picturing a grossly obese Olivia as Jabba the Hutt while wearing a straight face.
• Sainan-sensei channels his inner Conan Edogawa during his monologue when investigating the water Olivia splashed out onto the hall, complete with a silhouette of Conan standing next to him and a similarly-cheesy theme music:
  Only one truth prevails.

Episode 2

• Presumably, the Student Council's VP rallied the votes for her preferred president by turning into Sadako. The closeup on her rolled-down eye immediately afterwards helps to sell the impression.
• Hanako's signature "Green-Eyed Serve" is a reference of the Trope Namer of Green-Eyed Monster.

Episode 4

• Kasumi and Olivia's attempt at giving Hanako makeup to rival the visiting Lord of Pastimers accidentally turned her into an Expy of The Joker:
  Wasn't there a Batman villain that looks like that?
• Kasumi's BL novel is clearly based on Harry Potter.
• When Hanako proposes a title for Kasumi's novel, Crunchyroll translates it as "Anal Bum Cover", but a closer translation would be "Please Save My Butt", a clear reference to Please Save My Earth. Chisato's horrified reaction is because she's a fan of that series.

Episode 7

• Hanako trains her stag beetle to steal money from offertory boxes to a parody of the theme from Rocky.
• When plotting their theft of the Banana Papers, Kasumi whips out a getup that would make Arsène Lupin proud. It even comes with a stylized Calling Card.
• An excerpt of the Banana Papers reveals that Sainan-sensei was said to have to be hospitalized after ingesting potassium cyanide, all while a flashback of episode 1 is briefly shown, cheesy music and all. Potassium cyanide poisoning is a recurring method of murder in the earlier arcs of Detective Conan.
• The after credits scene has Hanako and Olivia sneaking up on Kasumi Solid Snake-style, and Hanako even yells "Snake!" when she accidentally blows up all three of them. When she blows everything up a second time, she yells "Snape!" instead.

Episode 8

• Olivia's phone game app Bacteri Go sounds suspiciously similar to another popular monster-collecting game.
• As Olivia talks about her and Hanako stealing hearts, she quotes "They stole your heart" while a Palette Swap of Inspector Zenigata appears in the background.
• As part of a punishment game, Hanako changes her hairstyle to look like Sailor Moon's and tries to punish Sainan-sensei in the name of justice, while Kasumi fires a Kamehameha at him. Sainan-sensei attempts to play along with Kasumi by yelling "Hidebu!" and pretending to get hit by it.

Episode 9

• Olivia's brother equates the excitement he gets from the scent of middle school girls to a tingle where he took an arrow in the knee.

Episode 10

• Upon hearing about Kasumi's presumed kiss, Hanako storms out of the clubroom with Olivia in tow, only to come back instantly dressing like a palette swap of The Spanish Inquisition. The flight cap and goggles on Olivia's forehead is a dead giveaway.
• Hanako's one-liner "Cinderella" song is the first sentence in the chorus of H2O's 1983 single Omoide ga Ippai, most known for being the ending theme of the anime Miyuki.
• Hanako's poster for the club's self-filmed movie is a direct shout out to A New Hope, complete with the signature Star Wars font and a recolored image of the Death Star in the background.
• When asking Kasumi why she wanted to make a sci-fi film, she admits she watched Star Trek, while doing the Vulcan Salute and with an image of USS Enterprise appearing in the background.

Episode 11

• Try convincing anyone at all that Agrippa's grandma is not an Expy of Professor McGonagall and see how many believe you.
• Olivia references the Seven Mysteries Murder Case of The Kindaichi Case Files when the main cast discovers the unconscious body of the all-boys school's student council president.

Episode 12

• Olivia downloaded her battle royale game from the Pineapple Store.

OVA

• Later on, when Olivia and Kasumi "congratulates" Hanako, she turns into Shinji Ikari in denim and a wig (her manga counterpart doesn't have one) while the backdrop changes to a cloudy blue sky.
• When Hanako's brother comments that he thought her classmates were "[her] imaginary friends", an image of Bloo shows up (saying "Mac!" no less, to make it even less subtle).