At least 3 and very likely "4" former cast regulars return for tonight's episode.
It wound up being 8 years together at County General for Eriq Lasalle and Noah Wyle.
Now after several years apart, the duo's back together for tonight's episode.
"It does feel like everything's coming full circle to have these two characters have some resolution to their relationship," said Wyle.
As the series winds down, LaSalle's just the latest original cast member to make a guest appearance.
"He started in on me about a year ago, asking when I could do it, so by the time it actually came to fruition, I was ready for it," LaSalle said.
In this episode, Dr. Carter's awaiting a kidney transplant at the hospital where Dr. Benton now works.
"There are a lot of things that I do think needed to be addressed and there was something about the relationship that needed to be explored," said LaSalle.
The episode also features guest star Susan Sarandon and former regular Julianna Marguiles.
As for anyone else? Yes, you will see that rascal that nurse Hathaway wound up marrying.
It's all part of a farewell tour for what's been a landmark show.
"To have an opportunity to come back and craft the final chapter to that experience feels extremely right," said Wyle.
"ER"'s final episodes continue through this month, with the series' two hour finale on April 2.