Bester

Bester was Serenity's original engine mechanic, portrayed by Dax Griffin. At some point before the events of Firefly (as shown in a flashback in "Out of Gas"), Malcolm Reynolds caught him having sex with a local girl, soon identified as Kaylee Frye, in the engine room. Mal demands to know what's wrong with the engine, and an increasingly flustered Bester is repeatedly embarrassed by Kaylee's knowledge of ship engine workings, then fired by Mal in favor of Kaylee.