As best I can tell, from my kids watching it over the last few years, it really doesn't matter. There's no real continuity. The first few episodes that aired, everything was "LEGO-fied." Buildings and cars, and "stuff" all had LEGO studs, etc. on them.
As the show progressed, though, it's cartoon versions of everything. Even the stuff that are sets, are cartooned versions of the sets. So instead of a very obvious LEGO studded rollercoaster, for example, it's just a stylized rollercoaster. Same exact design, colors, etc., just no studs, and not as blocky.
Back to continuity, there's an episode where the Friends meet up with the Pop Star (Livi), and they become friends with her. And it's clearly the first time they've all met. But then there is a different episode where they encounter Livi for the first time, and Livi unknowingly steals a song they've written, and the girls end up on stage with her. And it's clearly the first time they've all met. I could be confusing that with the time they met Livi (again for the first time), and it was an American Idol like contest.
Clearly, I've been paying more attention that I probably should to all of this.
Awhile back. There's a short, fat, red-hair girl that was also somewhat obnoxious. She appeared in a couple of episodes.