Glenn Groff, nicknamed "Thickhead," is a male Seguran from Ashwhite, presenting a stout build, pale skin, and the notably thick bony skull inspiring his moniker. As a Cosmo Academy applicant, he joins the final entrance examination: surviving 53 days aboard the derelict starship *Esperanza* alongside nine other candidates, though eleven applicants are unexpectedly present.

During the test, Thickhead displays an enthusiastic and diligent work ethic, frequently volunteering for shipboard tasks alongside the group. However, his actions create significant complications. He intentionally transmits incorrect instructions to fellow applicant Tadatos Lane, igniting confusion and conflict that exacerbates existing tensions. Furthermore, aware of critical, life-threatening safety hazards aboard the derelict ship – including bombs causing random explosions since boarding – he fails to report these dangers to academy officials. This negligence leaves the entire group exposed to escalating risk.

His ultimate fate diverges between source materials: the manga depicts his survival, while the anime adaptation concludes with him sacrificing his life to save the other applicants during a critical incident on the *Esperanza*.