She was excited at the prospect of meeting Bill Gates, but her excitement was nothing compared to that of Leonard, Howard, Raj, and (to a lesser extent) Sheldon, who believed that Penny’s announcement of Gates’ arrival was merely an April Fools’ joke.
Penny is the one who made the announcement that Bill Gates was coming to her job at the pharmaceutical company, as his foundation was working to expand its charitable reach.
Penny decided to just go ahead and let him believe that after he accused her of pranking him in the past, so Sheldon was out of the running to meet Gates.
The rest of the guys were decidedly not out of the running.