Hello,
Let's go talk about the fourth great episode of Boku wa Tomodachi ga Sukunai that finally present us all the other 3 members of the club (Rika, Yukimura and Maria) completing the cast of this show.
I think that completing the cast introduction by episode four is pretty good because leave plenty of time to develop their relationships, especially the one between Yozora and Kodaka that will be for sure the focus of this anime series.
They also finally completed to cover the second volume of the manga so everything past this point is completely new material even for me. I'm curious on how Kobato will manage to join the club in the following episodes...

This episode start with Maria's introduction, that is a 10-year old teacher of this school and the advisor teacher of the club. You can think of her just like Becky from Pani Poni Dash in terms of personality and her voice (same seiyuu of Index from the To Aru Majutsu No Index series) is whiny enough to portray her in a great way.
Then we have the surprise of this anime series that is Yukimura, she is a girl who tries to act as a male and stalk costantly Kodaka. The surprising part is that they managed to make her a lot cuter than what is presented in the manga.
In the end we have the creepy Rika, who for some reason is attracted by Kodaka much to the dismay of the other harem members. Rika is by far the most creepy out of the bunch, and I can really understand why she doesn't have friends...:P
Yes, this is configuring itself as a great comedy/harem series now that we have well 4 girls running to become Kodaka's girlfriend, especially considering that one of them is actively trying to jump over Kodaka.
Why 4 girls and not 6 girls you ask? Well, Kobato is his sister and Maria is just a child so they don't count in the girlfriend realm!
I wonder how will Kobato react if Maria will ever start to get clingy/affectionate to Kodaka...that would be a nice thing to explore and a possible source of comedy.

Talking a bit on the speculation side, I saw many images of Yozora Mikazuki with short hair around the net, but I don't know if they are canon material from the light novels or not.
I wonder if she'll ever cut her hair down, because that would be a rather nice change of look that I would definitely approve and like! I think she will look even more gorgeous with short hair!
Next episode seems to talk about Kobato again and will hopefully mark her first appearance in the club. I'm eager to see some Sena-Kobato interaction! :D

Concluding, Boku wa Tomodachi ga Sukunai may well be considered the best comedy series of this season thanks to the great cast, nice jokes and the decent protagonist!
See you soon,
feal87