Raj and Howard are sitting watching a monster movie from the 50's. Howard thinks it's lame because the effects are bad. Raj agrees, and wishes they could see real giant monsters. Sheldon overhears their conversation and comes up with an idea. He announces he's going to get plane tickets to take them to Japan to see real giant monsters. They go to Japan, much to the rage of Penny, who was to go on a date with Howard. She stows away on the plane. They go and meet Godzilla , who has been apparently a good friend of Sheldon for some time. Godzilla and the gang go to a harbor to hang out and remember some of Godzilla's greatest battles. Raj sits there, hoping he gets to to see him fight another monster. But, just in time,King Ghidorah , the 3-headed dragon, attacks Tokyo. Godzilla goes over to fight his arch-nemesis. The fight causes major collateral damage to the city.
Sheldon, wanting to help Godzilla, because Ghidorah's starting to win, goes over to the Japan Defense Force base and hijacks MechaGodzilla. Sheldon in MechaGodzilla fights Ghidorah. But, Ghidorah is way too powerful. To make matters worse, Rodan flies in and joins Ghidorah in the fray. Penny looks over and hijacks Kiryu, the nickname for one of the more modern MechaGodzillas, and intervenes in the fight. Ghidorah attacks, but Penny tears Ghidorah apart with no effort whatsoever and kills Rodan off-screen. She then turns on Sheldon. Sheldon asks for help from Godzilla prior to his beatdown, but Godzilla says, "I ain't getting involved in this. You're on your own." Penny goes over to Sheldon and tears apart his MechaGodzilla. She then warns him if he ignores another date, he'll be sorry.
After they get back to America, Sheldon apologizes for abandoning Penny for this trip. He has begun to realize, as he says, "Giant monsters are jerks". Raj, however, says he had a fun time and he wants to go again at some point. Everyone shouts, "NO WAY!"
- Even though the giant monsters vs giant robots flick, Pacific Rim is parodied in the title, the episode has nothing to do with Pacific Rim. It's a Godzilla parody. But, Pacific Rim is also a giant monster movie directed by Guillermo Del Toro.
- How Penny and Sheldon get through security in the Japan Defense Force is unknown.
- Even though Rodan teams up with Ghidorah in this episode, in the classic Godzilla movies, Rodan is on Godzilla's side.