Robert Sebree/NBCU Photo Bank

"That's crazy," ER star Sherry Stringfield told E! News in a phone interview. "I love it! That's so cool. I'm glad people could enjoy it."

Lisa Holme, the vice president of acquisitions at Hulu, told E! News the response to ER has been surprising.

"It has surpassed expectations for sure, both from a consumption perspective, but even more so from the zeitgeist that it has kind of picked up. We've launched other big, iconic shows on Hulu, from Seinfeld to Golden Girls to Will & Grace and others, and those have had their moments of excitement, but ER has been, I think, bigger and more sustained than we necessarily thought it was going to be…I think there was even more pent-up demand and nostalgia than we anticipated."