The final test to become Junior Bracer and Adventurer both involved getting things from sewer.
Before Cassius went away in the prologue, he entrusted Estelle with Black Orbment. Sage Lemuras (who is pretty much Avin's father figure) entrusted Avin with Sacred Treasure Kabessa before he passed away. Both are Chekhov's Gun.
The Guest Star Party Member in the first part of Chapter 2 (for AToV) or whole Chapter 2 (for FC) are another senior Bracer/Adventurer (Douglas and Agate) and a girl who develops a crush on one of the main duo (Archem and Kloe). When they were party members, the party must dealt with corrupt leader of the region who threatened the well-being of the girl's precious things (Meefas and Mercia Orphanage).
There's a Rival who actively prevents the party for ever advancing their adventures in the second half of the game. Said rivals are actually someone close to the main character. Not only that, near the end of the game, they engage an awesome duel with one of the main characters.
Weissmann asks Estelle to join Ouroboros with promise that she, Joshua, Loewe, and Renne can live happily together. This is similar to when Bellias-controlled silver-haired Mile asks Avin to join Octum's Apostles so he, Mile, and Eimelle can live happily together. Of course Avin and Estelle reject it.
Loewe sacrificed himself to weaken Weissmann by using Kernviter to invoke Taking You with Me after he knew that Weissmann was responsible for the Hamell tragedy. Madram sacrificed himself to kill Borgeid by using Dominique's Ring to invoke Taking You with Me after he knew that Borgeid was responsible for the Kanaphia tragedy.
The 3rd also invoked a little Mythology Gag to Legend Of Heroes IV: Loewe is Back from the Dead thanks to Lord of Phantasma and serves as her Dragon, and after the party defeats him, he disappears after a Tear Jerker exchange with Joshua, Estelle, and Renne (if one brings the latter two in the party, that is). Mile is Back from the Dead thanks to Lord Bellias and serves as his Dragon, and after the party defeats Octum, Mile disappears after a Tear Jerker exchange with Avin. The difference is that Mile isn't meant to die yet.
again from The 3rd: Kevin goes to Gehenna in order to save Ries, much like when Avin jumped to Hades in order to save Mile.
might be intentional since The 3rd was released shortly after PSP version of Legend Of Heroes V, but the whole point of the game is similar to Legend Of Heroes V's Tuning Forks Special Scenario. You get party members from clearing a dungeon or moving to the next chapter, can team up with the entire playables of the previous two games along with Original Generation, involves a boss rush, and a massive amount of grinding is required to reach 100% Completion.
Josette's S-Craft Wildcat is named after Legend Of Heroes III's Wildcat Bandits. It doesn't help that Capua family and Wildcat Bandits are actually good people.
You can find the complete Doll Knight books set in SC. Renne even referenced it when she was saved by the party, commenting that she's like Princess Tia who was saved by Pedro's Blue Knight. The books were originally from Legend Of Heroes V. There are some WMG concerning its existence in Zemuria.
While officially spelled Patel Matel by Falcom, given the use of furigana and the fact that Renne repeatedly states that it's the only father or mother she needs it should be written Pater Mater, Latin for 'Father and Mother'.
Is it "Loewe" or "Löwe"? Even Falcom sources disagree at times. Both work, though (they're the same word in German). XSEED chose to go with "Loewe".
A bit of debate also springs up around the title for the agents of Ouroboros. The title is given in kanji as 執行者, shikkousha, which strictly speaking is a term variously applied to "those who perform, execute or serve business" (and also actual executioners) and also has Buddhist connotations for righteousness and the pursuit of enlightenment. However, the kanji are always accompanied by furigana, in katakana, indicating that the word the characters are saying is "Legion", which is meant to be the actual, in-universe term spoken by characters. The problem, of course, is that "legion" is a term for a unit of soldiers and not an individual person, and doesn't really carry the concept of the kanji forward regardless. While a majority of western fans currently stick with the indicated title from Falcom, some do use other terms to try and convey the kanji better - Enforcer, Legionnaire, Executioner and the like have all cropped up over the years.
During the scene at the end of FC wherein Joshua and Weissmann confront one another, the XSEED translation uses both "Enforcer" and "Legion".
Relatedly, the Ouroboros codename for Enforcer Fifteen runs into a problem as well. For all the other Enforcers, the "intended" English version of their codenames is given in secondary sources, particularly promo websites - "Sword Emperor" for 剣帝 (kentei), "Phantom Thief" for 怪盗紳士 (kaitou shinshi) and so on. With Fifteen, however, all we have is the kanji - 殲滅天使, senmetsu tenshi. The "angel" part is obvious, but there have been some debates over the best way to render "senmetsu" (which, most literally, means "total destruction/slaughter/annihilation/etc; Apocalypse How in a can, basically). "Angel of Extermination" is one of the more common translations, though some fans feel this is a little awkward; others go with "Annihilation Angel" or "Angel of Slaughter". XSEED has not yet announced an official translation for the term.