I applied through a recruiter.
It was a standard first round interview with many technical questions. The second round was a deep dive into projects on the resume and defense of the choices on such a project.
The following metrics were computed from 22 interview experiences for the SpaceX Mechanical Engineering Intern role.
SpaceX's interview process for their Mechanical Engineering Intern roles is fairly selective, failing a large portion of engineers who go through it.
Candidates reported having very good feelings for SpaceX's Mechanical Engineering Intern interview process.