The only thing better than enjoying a new episode of Grey’s Anatomy? Enjoying a new episode of Grey’s Anatomy along with millions of other people tuning in to the show’s must-see drama. Each of the hours featured in part one of our list below was the highest-rated episode from its season, meaning that during these Thursday nights (and two Sundays), a whole lot of fans got to experience the magic of Shondaland’s longest-running series together.

And even if you’ve watched Grey’s from beginning to end multiple times over the years, you probably don’t know how all the show’s most popular hours came to be. Read on for some fun behind-the-scenes trivia from the first 11 seasons of our fave medical series.

Season 1, Episode 9: “Who’s Zoomin’ Who?”

In the first season finale of Grey’s Anatomy, the docs performed a secret surgery on Richard, George got an STD, and Addison arrived in Seattle in style, putting an end to Meredith and Derek’s happy romance.

Fact No. 1: Despite its shocking cliff-hanger, this episode wasn’t originally meant to be the finale. Shonda Rhimes revealed in 2005 that the crew shot five more episodes to air afterward, but when ABC execs decided they wanted Grey’s and Desperate Housewives to end their seasons on the same night, they moved those other five episodes to season two.

Fact No. 2: To convince the network to allow an STD storyline, the Grey’s Anatomy writers created a “Top 10 Reasons We Can Give George Syphilis” list. Per writers Gabrielle Stanton and Harry Werksman Jr., arguments included “ER hasn’t done it.”

Season 2, Episode 16: “It’s the End of the World”

The all-time highest-rated episode of Grey’s aired after the Super Bowl and saw Meredith put her hand on an unexploded bomb inside a patient’s chest.

Fact No. 1: Director Peter Horton told Shondaland that several unforgettable moments were improvised, including paramedic Hannah (Christina Ricci) leaving a bloody handprint on the OR wall.

Fact No. 2: Hours of screaming at the top of her lungs caused Jillian Armenante (Mindy, the patient’s wife) to lose her voice, as she told Shondaland.

Season 3, Episode 17: “Some Kind of Miracle”

After Meredith nearly drowned, she unconsciously reconnected with her dying mom while the doctors tried to save her life.

Fact No. 1: According to Marti Noxon, who co-wrote the episode with Shonda Rhimes, the Grey’s Anatomy team “hotly debated” the moment when a grieving Cristina left the hospital during Meredith’s treatment.

Fact No. 2: The episode was directed by Adam Arkin, who’s no stranger to medical TV dramas; he’s also an actor best known for starring in Chicago Hope.

Season 4, Episode 1: “A Change is Gonna Come”

In this season premiere, the former interns (minus George) began their residencies, Meredith got to know her half-sister Lexie, and Callie struggled to be a good chief resident.

Fact No. 1: Actress Chyler Leigh (Lexie Grey) initially found it intimidating to join the Grey’s Anatomy cast and told The Sydney Morning Herald, “It was like coming into somebody else’s group or circle. … It was a little daunting in the beginning.”

Fact No. 2: Viewers noticed that in the scene when Izzie defibrillated a deer, she put her stethoscope on backward. Oops!

Season 5, Episodes 1-2: “Dream a Little Dream of Me”

This two-part season premiere is best remembered for Owen Hunt’s dramatic arrival and Cristina being impaled by an icicle.

Fact No. 1: Owen was only supposed to be a recurring character, but his high energy and chemistry with Cristina caused Grey’s to promote him to a series regular.

Fact No. 2: This episode was nominated for an Emmy Award for Outstanding Makeup.