I think that Alejandro and Sierra are fill-ins.

Think about it.
Alejandro has piercings. He has a beard and epic hair. And he is bad.
Duncan has piercings. He has a beard and epic hair. He is bad.

Sierra is obsessive. She has a ponytail..
Beth is obsessive. She has a ponytail.
Anyone else see what I mean?
Alejandro is a fill-in for Duncan, and Sierra is a fill in for Beth.

Wow, I must be very pumped for TDM.. not a día goes por that I don't think about these two.
Sierra: Your'e sweet ^^
Me: ^^
Alejandro: *looks at me with a freaked out expression on his face*
Me: Hee ^^
Alejandro -.- tu creep me out.