Abridged Arena Array: Throughout PSU's run, players have sought out the Free Missions with the most efficient EXP gain. The lobbies for those missions would be accordingly packed full as well. In Vanilla PSU, this first happened to "Plains Overlord," then to "The Mad Beasts," then to "Endrum Remnants." When AotI was released, this honor went to "White Beast," and remained so whenever an event wasn't going on—to the point that PSU itself was derisively nicknamed "White Beast Universe" as no one seemed interested in running any of the other missions in the game.
This tendency prompted Sega to introduce the "GUARDIANS Boost Road," encouraging players to run chains of other missions for greater gains compared to spamming a single mission over and over.
Moral Event Horizon: Light Master Dohgi Mikuna is revealed to have crossed this a long time ago when Ethan discovers that Dohgi had been using Mirei Mikuna's gifts of divination for rogues and other criminals, receiving payments for doing so. Long before that, Dohgi placed a Mark of Light on Karen, Mirei's twin sister, to bolster Mirei's vitality; the Mark saps Karen of her abilities, which leaves her unable to use TECHNICs. During Episode 1, Doghi attempts to finish the job by sacrificing Karen's life in order to prolong Mirei's. Mirei tries to stop him, but is met with a powerful Technic that kills her.
“Stop Having Fun” Guys: You don't have to do much to get booted from a party. Especially when you're at the end boxes in certain missions.
They Wasted a Perfectly Good Plot: A minor example. Importing a character from Phantasy Star Portable to its sequel results in no significant storyline differences. Even characters whom you've met before in the first game don't seem to recognize you, and the only one that does is Vivienne, who's an optional partner in PSP2 (unlike, say, Tonnio and Liina, both of whom are met at the start of Chapter 2 and aren't optional), and even then that only amounts to a couple of changes to her dialogue upon meeting you. The fact that there isn't even an attempt at an explanation for it is also bothersome. As such, there are players that feel that SEGA dropped the ball in this regard, but at least importing still nets you a unique title and some neat items.