Superman: Legacy' writer-director and DC Studios co-chief James Gunn is expanding the new DC universe with three new actors joining the cast, reports 'Variety'.

The actors are Nathan Fillion ('Guardians of the Galaxy Vol. 3'), who'll play Guy Gardner, one of the figures known as Green Lantern; Isabela Merced ('Dora and the Lost City of Gold') will appear as Hawkgirl; and Edi Gathegi ('X-Men: First Class') will be seen as Mister Terrific, 'Variety' adds.

Gunn had cast David Corenswet ('Hollywood') as the titular Man of Steel two weeks ago, alongside 'The Marvelous Mrs Maisel' star Rachel Brosnahan as Lois Lane.

At a press presentation of the new DC Studios slate back in January, according to 'Variety', producer and DC co-chief Peter Safran said the film would focus "on Superman balancing his Kryptonian heritage with his human upbringing. He is the embodiment of truth, justice and the American way. He is kindness in a world that thinks of kindness as old-fashioned."

The news that 'Superman: Legacy' will include superheroes other than the last son of Krypton is a strong indication that Gunn intends to re-launch the DC cinematic universe as a fully-formed entity, rather than re-build it one superhero at a time.

Fillion, says 'Variety', has often appeared in Gunn’s films, starting with the filmmaker's 2006 horror-comedy 'Slither'. His character, Gardner, will be just one of several people in the new DC Universe to wear the emerald ring that imbues its wearer with the powers of the Green Lantern.

As Hawkgirl -- masked, winged and fond of medieval weaponry such as swords and maces -- Merced will be embodying one of DC's oldest superheroes, who first appeared in 1940, notes 'Variety'. (Aldis Hodge played Hawkgirl's counterpart, Hawkman, for the character's live-action feature debut in 2022's 'Black Adam'.)

Along with playing Darwin in 'X-Men: First Class', 'Variety' adds, Gathegi most recently was a standout on Season 3 of Apple TV+'s 'For All Mankind'. He’ll play Michael Holt, an ingenious inventor who operates as Mister Terrific with the multi-purpose, mechanical 'T-Spheres' he created.