I had a return offer from an earlier internship and so, my interview process was fairly easy and straight forward. Just a relatively formal technical chat/interview with the hiring manager of the new team and that was it.

Took about 4 weeks between applying and an on-site interview. Applied online, got a call for a screening interview, then asked to come in for an interview. The screening interview was done by a recruiter and was a bit awkward as they only asked questions that could have easily been answered by a quick look at my resume. No behavioral questions. I was contacted a couple weeks later to come in for an interview with "hiring managers." I emphasize "hiring managers" because there actually wasn't a single hiring manager present. Instead, it was 3 scientists from the group I was interviewing for. In this interview, I was asked both technical and behavioral questions. The one caveat to this whole experience, though, was that it wasn't so much an interview as it was a dissertation defense. Questions were directed towards a position that was not as it was described on the online application. Overall, the whole experience was a bit disappointing, especially for a company of this size and capability.