We report on a simple, rapid, and room-temperature undergraduate-level experiment for gold nanoparticle synthesis, analysis, and utilization as a catalyst for the sodium-borohydride-assisted reduction of methylene blue and Congo red dyes. Typical procedures toward gold nanoparticle formation require an elaborate, lengthy synthesis (some requiring 1 h for completion of nanoparticle formation and ripening), whereas faster methods frequently yield inhomogeneous or catalytically inferior gold nanoparticles. This situation limits the usefulness of gold nanoparticles as rudimentary nanochemistry teaching tools in time-restricted undergraduate laboratories. The rapid gold nanoparticle synthesis presented herein utilizes ascorbic acid or sodium borohydride as dual reducing/capping agents to produce catalytically active gold nanoparticles at the "speed of mixing" under ambient conditions, allowing preparation and characterization to be performed within a single laboratory period. Furthermore, whereas most gold nanoparticle syntheses require rigorously cleaned glassware to avoid contamination and irreproducibility, the devised undergraduate experiment reported here alleviates this burden by employing disposable reaction vessels. Thus, this undergraduate-level laboratory experiment is designed to provide a meaningful introduction to metal nanoparticle synthesis and application while simultaneously being accommodated by a typical 2-4 h laboratory period, providing much-needed teaching assistance in the growing field of nanomaterials education.