What's the deal with Cocona creating a fireball and throwing it with one of her attacks? She's a Reyvateil who is just beginning to mature and said fireball is the most basic attack spell for Reyvateils.
Both Luca and Cloche have several Awesome Moments though Luca's are often far more low key and "behind-the-scenes" despite being just as noteworthy as Cloche's (as the two save each other multiple times in Phase 3). This exactly parallels Luca's Level 4 Cosmosphere in that she doesn't mind stepping up to fight when she has to, but is content with giving Cloche the spotlight (though she in turn makes sure to give Luca her due credit).
The same can be said for their Character Development (and why Luca remains a more divisive character) as Cloche's is very overt while Luca's is very subtle. This again matches up to their sun and moon theme, respectively.
Luca's Venus Torial costume highly resembles the Linkage armor worn by both Shurelia and Tyria. Why does Luca get something similar? Because she's the Maiden of Homura and is directly connected with Frelia, who is never seen in Linkage armor.
Why is Cloche so good with kids? Because she still cherishes the memory of her one friend who was made to "disappear" after accidentally meeting with her in the Grand Bell Hall.
In Luca's Level 5, she explains to Croix that Therapy isn't just listening to a person and always agreeing with them, but taking a good look at their subconscious and telling them what they need to hear. This is evident in the Dive Therapy mini-game as simply Talking to each IPD without first observing her current state will almost always result in failure.
Despite the fact that Cloche is part of the group that oppressed and did horrible things to the I.P.Ds while Luca is the one that seems to care for them and cure and saved them, they start a fan club for Cloche instead. It makes sense in terms of game mechanics, as Cloche is the only one capable of using Replekia, which draws on the powers of the I.P.Ds.
Should the player complete Luca's Cosmosphere, her ultimate Song Magic unleashes a Kill Sat beam from Sol Marta, which is the final dungeon. So using that Song at any time in the final area (and especially against the final bosses) causes Sol Marta to somehow fire on itself.