6 details you may have missed on Sunday's 'The Walking Dead'

This is a big reveal for comic-only fans. Mercer's first name is never mentioned in the comics.

Michael is also the first name of the actor who plays Mercer, Michael James Shaw.

Hershel Rhee was seen crouched down by a pile of stones at the Hilltop. That's where his father, Glenn, is buried.

His father was likely fresh on his mind after his recent encounter with Negan. Hershel just learned that Negan was the one responsible for the death of his dad. Negan told Hershel that they still have unfinished business and that he should feel free to seek him out one day in the future to settle things.

If you go back to season 11, episode 14, you can see the exact moment Hershel loses the hat.

17 minutes into the episode a Commonwealth soldier takes it off his head and tosses it to the ground.

Hershel was probably too upset with Negan — and concerned with staying alive — to worry about picking it back up. But it was that piece of evidence that likely let Lance know that Maggie and the Hilltop community was keeping something from him.

Khary Payton's bow on Sunday's episode immediately brought to mind a behind-the-scenes image of the actor on set of the series on season 10, episode 15.

If you thought Ezekiel's underground hospital seemed absolutely random, it's not. The thought process behind helping the less fortunate goes back to his core beliefs from when we first met him on season seven.

"From the very beginning, he has always been about pulling your own weight," Khary Payton said of his character, Ezekiel, in pre-taped video on "Talking Dead."

"When he started in the Kingdom, one of the first things he said to Carol and Morgan was, 'You take from the well, but you replenish the well. Take what you need, but also, you have a responsibility to give back to the community," Payton added of why Ezekiel chooses to set up this hospital after he's given a second lease on life at the Commonwealth.

"Drink from the well, replenish the well" is written on the wall of a room where Carol stays on season seven, episode two, titled "The Well."

The person Tomi does an appendectomy on is Theresa, an original member of the Kingdom who you can spot at the fair on season nine, episode 15.

According to series' aftershow "Talking Dead," Payton suggested that Theresa should be the patient.

"She represents the Kingdom for Ezekiel," Payton was quoted as saying on screen on "Talking Dead." "She's this precious thing that somehow survived."