* AngstWhatAngst: Yotsuba was either orphaned or abandoned overseas, then taken in and raised by Dad. At least partly justified, since Yotsuba seems to have been too young to remember her real parents, and anyway, what matters to this story is that she's happy and [[strike: well-adjusted]] [[strike: normal]] healthy ''now''.
* EnsembleDarkhorse: Cardbo, the cardboard robot, who got an action figure despite having (at the time) appeared only once, and has even ascended to the noble position of [=Official Mascot=] of Amazon.co.jp. Just don't tell Yotsuba [[spoiler:it's Miura in a costume made for a school assignment]].
** Now with his own ''customizable'' plastic model! [[http://www.collectiondx.com/news_item/2912/danboard_kit_kotobukiya BEHOLD!]]
* FanPreferredCouple: There is little to no romance in the series itself but Koiwa X Fuuka is easily the fan favorite. RuleThirtyFour is generally frowned upon when it comes to this series but they obviously exist, and probably 90% of them are on these two. It helps that most of the {{ship tease}} that exists in the manga at all are between them.
** For [[YuriFan some fans]], Asagi and Torako.
* FanNickname: Yotsuba appears on [=4chan=]'s 404 Not Found page, and is thus known as "404 Girl". A recurring character that Yotsuba sometimes plays with is called "Dotty" by the fans, after her eyes being always drawn as 2 dots.[[note]]Was unnamed for a good while, but was eventually given the nickname "Mi-chan" in the chapter "Yotsuba & the Sandpit".[[/note]]
* HollywoodHomely: Fuuka is often unfavorably compared to Asagi.
* HollywoodPudgy: Fuuka is frequently stated to have fat legs, and is even teased about this by Asagi and their mother. Look at a picture of Fuuka alongside any other teen girl character in the series, and see if there's ''any'' major difference in their body types.
** Then again, Asagi and mom are jerkasses at times, so they could just be messing with her.
* LesYay: Asagi is never seen socializing with anybody outside of family and her neighbors--except for Torako. Asagi and Torako also love to go on long outings together, and [[YuriFan some people]] feel those show all the telltale signs of actual dates. It helps that the outings we know of, do indeed seem like date spots; an Okinawan beach, a Hot Air Balloon race, and a Firework Display. Its also shown that these outings are always, or at least planned, for just the two of them.
** When Jumbo demands to know who "[[GenderBlenderName Tora]]" is, after Yotsuba draws a picture of Asagi and her, Yotsuba describes her in a way that sounds like Tora is Asagi's boyfriend, much to Jumbo's [[HeroicBSOD dismay]]. It becomes something of a running gag later on.
* MemeticMutation: Yotsuba is used as a mascot by some ImageBoards, most prominently 4chan, which uses a clover as its logo and runs on a modification of Futaba called Yotsuba.
** In addition, MemeticMutation is exemplified ''within'' the series by the teddy bear Duralumin, who shares a name with a metal alloy but is really Yotsuba's [[{{Malaproper}} mispronunciation]] of ''Ena's'' stuffed bear Giulietta.
* SacredCow: Don't even mention anything that involves RuleThirtyFour images of Yotsuba of any sort to Anonymous.
** Thankfully made easier by the fact that there isn't all that much to begin with.
* {{Shipping}}: A popular ship is Koiwai x Fuuka, prompted by their multiple interactions (including classmates asking Fuuka if Koiwai is her "husband") and hinted at in Azuma's proto-comic for ''Yotsuba&!'', "Try! Try! Try!". The multiple blush-inducing situations that Fuuka experiences around Koiwai (including the paper-cup telephone [[NotWhatItLooksLike conversation]] and a comment in Chapter 67 about how her [[BigOlEyebrows eyebrows are cute as they are]]) do not help this. That Azuma in a side comment was "scared" by Fuuka's classmates finding Koiwai attractive hasn't deterred shippers.
** In chapter 61, Koiwai gives Yotsuba a "helicopter ride" (swinging her around by the arms so her feet leave the ground). Then Asagi lines up to try it, and seeing them circling each other hand in hand, Torako comments "They seem to get along together really well"... Ooh, Azuma-sensei, you [[ShipTease ship-teasing]] ''devil'' you...
*** A few chapters later, Koiwai teases Jumbo with a picture of it.
** The [[LesYay Asagi x Torako]] shipping.
** [[HoYay Koiwai and Jumbo's]] closeness with each other have garnered a few fans for the ship. Some panels with the two of them with Yotsuba make them look like an actual family.
** Miura tends to get shipped with [[LesYay Ena]] or, more frequently and more ''[[{{Squick}} disturbingly]]'', [[HugeGuyTinyGirl Jumbo]].
** There has been some Yanda x teenaged Yotsuba, since if she was older their relationship would have all the makings of a SlapSlapKiss romance.
* ShipToShipCombat: Hardly bloodthirsty but it pops up on occasion.
** Since the Balloon arc, some have started to prefer Koiwai with Asagi over Fuuka. Then of course there are those who prefer [[ShipMates Asagi with Torako and Fuuka with Koiwai]].
** {{Shipping}} vs. NoYay: quite a few people prefer the ship tease to stay subtle and go no where.
* SweetDreamsFuel: No one can resist Yotsuba's cheerful attitude toward her life, NO ONE.
* UnacceptableTargets: Almost the TropeNamer. Even in [[EvenEvilHasStandards the darkest depths]] [[ImageBoards of the Internet]], Yotsuba Is Off Limits.
* ViewerGenderConfusion: Torako and Miura.