Fillion was initially set to appear as Simon Williams a.k.a. Wonder Man, a scientist who eventually becomes an actor and stuntman in the comics.
Watch how Phil reacts when his daughter Hayley (Hyland) brings her new boyfriend, Fillion's Rayner Shine, to Thanksgiving dinner.
It is assumed that the actor will play Simon Williams or Wonder Man who used his superpowers to star in Hollywood movies.
The couple made no attempt to hide the romance with many of their photos together posted on the actress' Instagram page.
Showrunners Terence Paul Winter and Alexi Hawley respond to report that an established drama will kill off its co-lead this season.
The 'Castle' actor expresses his interest in playing either Ralph Hinkley or Booster Gold or another DC comic character Ambush Bug when asked which superhero he'd like to tackle.