When I was in undergrad (20ish years ago) it was absolutely possible for a motivated student to graduate at a highly accelerated rate. I know someone who had approximately 5 semesters worth of classes done at the end of his freshman year, having taken about 40 credits worth of classes each semester (12 credits was considered "full time" and you needed to average slightly more than that per semester to graduate in 4 years in most degrees).
He was able to do this because:
1. Only foreign language classes and lab sciences had class-participation requirements
2. All classes published a syllabus so where possible he could start the major projects early
3. Most of the lower-division classes were a joke to a smart and motivated person anyways.
4. He convinced an academic advisor to sign off on it (this was arguably the hardest part).