Now Playing: Anthony Mackie opens up about 'Avengers: Infinity War'

Now Playing: Letitia Wright discusses 'Avengers: Infinity War' and her 'Black Panther' character

Now Playing: New trailer for 'Avengers: Infinity War' released

Now Playing: Prince may have unknowingly taken counterfeit medication laced with Fentanyl: Authorities

Now Playing: No one will be criminally charged for Prince's drug overdose, prosecutors say

Now Playing: 'GMA' Hot List: Anthony Mackie teases Mark Ruffalo as an 'institution of trouble'

Now Playing: What to expect from the 2018 Tribeca Film Festival

Now Playing: How Michael Strahan wakes up happy

Now Playing: Tina Turner bio-musical comes to London

Now Playing: Evan Rachel Wood opens up about 'Westworld' season 2

Now Playing: 'Avengers: Infinity War' star names co-star as ultimate class clown

Now Playing: Your exclusive 'Scandal' finale sneak peek

Now Playing: Royal fans camp outside hospital awaiting Princess Kate

Now Playing: Meghan Markle joins Prince Harry at high-profile event

Now Playing: Kerry Washington on how Tony Goldwyn supported her leading 'Scandal'

Now Playing: Who are the most ardent, dedicated royal fans?

Now Playing: 'Chappaquiddick' star on his new role as Sen. Ted Kennedy

Now Playing: Michael J. Fox opens up about 'Designated Survivor' on 'GMA'

Now Playing: 'Girls Make Beats' aims to help more women break through the music industry

Now Playing: Little girl's reaction to Princess Tiana doll will melt your heart