In the film, Gru teams up with his long - lost twin brother Dru in order to defeat a new enemy named Balthazar Bratt, a 1980s child actor who grows up to become a villain. Steve Carell, Miranda Cosgrove and Dana Gaier reprise their roles of Gru, Margo and Edith from the first two films and Julie Andrews returns as Marlena, Gru 's mother from Despicable Me (2010). Kristen Wiig and Steve Coogan return from Despicable Me 2 and Trey Parker, Jenny Slate and Nev Scharrel (replacing Elsie Fisher as Agnes) join the cast. Russell Brand does not reprise his role as Dr. Nefario from the first two films.
who is the voice of agnes in despicable me 3
Elsie Fisher