Timothée Chalamet is also immersed in a "huge vat of chocolate" for one scene.
Flora Nolan makes a cameo in a vision in the mind of Cillian Murphy's scientist J. Robert Oppenheimer.
Hayley Atwell enjoyed Tom Cruise and Christopher McQuarrie's "alive" way of working.
Alexandra Shipp was floored by the scale of the Barbieland set.
Tom Cruise may be de-aged in future Mission: Impossible films.
Hayley Atwell felt the cameo "didn't serve Peggy well".
The Barbie producer called the filmmaker "one of the great directors of our generation".
Oppenheimer and Barbie open in cinemas on 21 July.
Hugh Grant was first seen as the Oompa Loompa in the film's trailer on Tuesday.
The trio joined previously announced stars David Corenswet and Rachel Brosnahan.
Dolittle's failure helped Robert Downey Jr. and his producer wife re-evaluate their priorities.
Greta Gerwig previously worked with Timothée Chalamet and Saoirse Ronan on Lady Bird and Little Women.
