British actor Barry Sloane plays Joe "Bear" Graves.
Colombian actor Juan Pablo Raba plays Ricky "Budda" Ortiz.
Follow the Leader: After Seal Team debuted with a female CIA analyst as a regular character, Six introduced its own female CIA analyst in its second season.
Dawson Casting: Katherine Howard was (tragically) only sixteen or seventeen when she married Henry, and nineteen when she died. The original West End cast has thirty-year-old Aimie Atkinson in the role. Justified considering Aimie looks considerably young for her age.
Dyeing for Your Art: Some of the actresses have dyed their hair to achieve the look associated with their respective queen, notably Howard's black and pink ombre. Some do not, instead opting to use wigs or extensions. Aimie Atkinson (West End/album Howard) and Sam Pauly (Broadway Howard) went into this on Aimie's Thespies show, talking about how the constant dyeing and re-dyeing to keep the pink tips bright and unfaded fried their hair.
"Alternate massive," for when three or more alternates (or "swings," since they're all trained to cover all six roles, rather than understudying one or two) have to cover the main roles. More visible in "Six" than in most shows, since the alternates all have unique costumes. For a show with only six speaking parts, they seem to often need emergency covers, and it's not uncommon for actors from prior casts or simultaneous casts to do emergency covers, such as Jen Caldwell from the UK tour cast covering for the West End cast, or Maiya Quansah-Breed covering for the UK tour cast after she'd already left the West End cast.
When one of the swing actors has gotten to perform all six roles onstage, that's called "Swingo."
The Other Marty: Out of the premiere West End cast, only two, Natalie and Aimie, were part of the original cast. The other four - Renée Lamb, Christina Modestou, Genesis Lynea, and Izuka Hoyle - have since moved on to other projects. However, Renée and Genesis have reprised their roles on separate occasions.
Romance on the Set: Genesis Lynea (the original Anna of Cleves) and Aimie Atkinson (Katherine Howard) are currently dating.
Underage Casting: Catherine of Aragon, normally played by women in their early twenties, was fifty when she passed away. Anne Boleyn and Catherine Parr, also played by women in their twenties were in their thirties when they got married to Henry.
Samantha Pauly, the US Howard, took a leave from the show while it was touring in order to play Evita on the West End. While she was in the UK, she was approached to do an emergency cover for the West End cast. It ended up not happening because her work visa only covered her for playing in Evita at one specific theater, not for playing in any other shows.