On the other hand, he's kind of a cocksucker and he is ruining Challenge Day, so fuck him.
There's a nice shot here where Mona considers Emily, and vice versa, while Ashley's voice can be heard reading:
"This exercise is about discovery. Discovering yourselves, and discovering your classmates..."
I love how so many of the milestones these girls have set for them has to do with making amends to Ali's victims. I mean, they were Alison's victims too, of a certain stripe, but part of cleaving to Ali was making sure that she didn't come after them, and the shit kept rolling downhill. They were de facto quislings about a lot of that shit. (Where it came from, above Ali on that inclined plane of rolling shit, we have yet to learn. I've got some ideas. This show's allowed to do a lot worse stuff to Ali than it can to the main four, if you think about it, and they've taken a fair amount of pretty horrible abuse already.)
But so Mona and Lucas, in addition to being awesome characters and fun to watch, are also pretty symbolic of the Liars' development. So much about growing up has to do with taking out the things you're least proud of and the things that make you feel the worst or the scaredest or the ugliest and actually just looking at it, figuring it out, so that it can't shame you anymore. In alchemy, actually, the word albedo refers to this process, this washing-and-rewashing, and it's the most important step.
So Lucas has been taken out and looked at by all of them, pretty much, and washed clean -- no pun intended -- and now it seems like it's Mona's turn, first with Spencer and now with Emily, seeing those other parts of her that Hanna sees.
(And how interesting it is that Hanna, the neediest and the least secure of them, is the first one to ever do this work? She was the first one to work with Therapy Anne, the first one to break through, the first one to bring in any of these people. I have this theory that sometimes it's hard to see the healthiest people for what they are, because they're always churning up so much shit in the interest of becoming more honest and more healthy, that it just looks perpetually crazy. Which is not really functional either, so it all flips over again and doesn't matter, but: Hanna Marin, is she an artist? Maybe.)