In the fourth of four semi-final rounds, three more of the contestants use the $50,000 prize money to develop their inventions. In this episode Doug Hall mentors and judges the three semi-finalists.
| Name | Type | Role | |
|---|---|---|---|
| Jennifer Safuto | Guest Star | ||
| Joseph Safuto | Guest Star | ||
| Sharon Clemens | Guest Star | ||
| Janusz Liberkowski | Guest Star |