Whedonverse appearances: Angel as Winifred ‘Fred’ Burkle/Illyria; Dollhouse as Dr Claire Saunders/Whisky; The Cabin in the Woods as Lin; Much Ado About Nothing as Beatrice
Marvel appearances: Agents of SHIELD: ‘The Only Light in the Darkness’ as Audrey Nathan.
Amy Acker is one of Whedon’s favourite actresses, clearly, as they have worked together many times – first of all as Angel‘s Texan science whizz Fred. She then appeared in Agents of SHIELD as Phil Coulson’s old flame, Audrey (“the cellist” as mentioned in The Avengers).
J August Richards
Whedonverse appearances: Angel as Charles Gunn.
Marvel appearances: Agents of SHIELD as Mike Peterson/Deathlok
J August Richards was a regular on seasons two to five of Angel, after arriving at the tail end of season one, as street kid-cum-vampire hunter Gunn. He later joined the Marvel universe as tragic villain Deathlok over a run of episodes of Agents of SHIELD‘s second season.
Whedonverse appearances: Buffy the Vampire Slayer/Angel as Daniel ‘Oz’ Osbourne.
Marvel appearances: Iron Man 2 as Expo Guest (Uncredited); Guardians of the Galaxy as Howard the Duck.
Seth Green is most known to Whedonites as loveably laconic werewolf Oz on Buffy (and a single guest spot on Angel). He is also a friend to the MCU, as he cameod in Iron Man 2 and
then appeared in Guardians of the Galaxy as the infamous Howard the Duck – a role he reprised in the Ultimate Spider-Man cartoon.