My recruiter set up an interview date. I was walked in by the recruiting company's account executive and introduced to the Creative Director. After speaking with him for a few minutes (mostly chatting about the company) I was introduced to the Front End Development team lead. From then on the questions got more technical, but nothing over the top. All were applicable to the job - no curve balls like Google, etc, are fond of.
The office and people were exactly what I expected for an agency - very laid-back, most were wearing shorts/sandals, one dev drinking a beer at ~2pm (it was a particularly stressful week, he said).
Despite knowing the company had a casual environment, my recruiter still talked me into wearing a suit for the interview. I was given some grief about that prior to leaving, saying that was the new dress code going forward.
Most applicants have a follow-up interview w/ the CEO, but he in the middle of a lengthy vacation when I applied and they needed someone in immediately, so no follow-up interview for me. I was just given an offer through my recruiter and on-boarded within 2 weeks.