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4. Cher and Meryl Streep
Costarring again in this summer's Mamma Mia! sequel (as a mother and daughter pair, despite their 3-year age difference), these two icons have been pals since 1983 when they shared the screen in Silkwood. The Oscar winners were reportedly inseparable on the musical movie's set and even shared a smooch on the red carpet at the film's premiere.