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Jesse Williams and Sarah Drew are very close.

“We developed something really special on the show, which is a rare opportunity with this many cast members [starring on a show] going on for this long,” Williams told EW at the shoot for this week’s Grey’s Anatomy cover.

It makes sense that the actors developed such a strong bond considering the pair’s Grey’s Anatomy characters, Jackson and April (or “Japril,” as they’re known by fans) went from being best friends to married to bitter divorcees to friendly co-parents in the span of nine seasons.

Japril became a fan favorite, but Williams notes that it wasn’t always that way. “Fans hated us at first — I think it’s important for people to realize that,” Williams said. “April and Jackson are opposites in many, many ways. In their belief systems and many other ways, so it was clunky.”

Watch the full clip of Williams discussing the Japril story arc above, and make sure you check out the cast of Grey’s Anatomy on not one, but six different covers for EW’s latest issue, and the #7DaysofGreys tag for all of EW’s content celebrating the iconic show’s 15th season.