Bob Hope and Bing Crosby. Bud Abbott and Lou Costello. Martin Scorsese and Robert De Niro…. With these movie duos, sometimes you can’t think of one without the other. And in some cases – Fred Astaire and Ginger Rogers; Stan Laurel and Oliver Hardy – you just need their first or last names.

To determine a list of the most iconic movie duos, 24/7 Tempo reviewed information on collaborations from sites including IMDb, an online movie and TV database owned by Amazon; Rotten Tomatoes, an online movie and TV review aggregator.com; Screen Rant; and Backstage.

To become an iconic movie duo, a pair has to have that elusive element – chemistry. In the examples of Hope and Crosby and, later, Dean Martin and Jerry Lewis, the chemistry worked because each had a defined role – one was a romantic, singing lead, while the other played it for laughs.

George Burns and Gracie Allen, who were married in the 1920s, made their partnership work on stage, radio, motion pictures, and television until Allen passed away in 1964. Other male/female collaborations on film have led to romantic involvements offscreen, such as Spencer Tracy and Lauren Becall and Woody Allen and Diane Keaton. (Sometimes involvements work out for the long term. These are the 30 longest-lasting celebrity marriages.)

Male/female partnerships that have remained professional, on the other hand, include those of Drew Barrymore and Adam Sandler and Emma Stone and Ryan Gosling.

Click here to see the most iconic movie duos of all time

Some of the more noteworthy bromance pairings include Paul Newman and Robert Redford, Dwayne Johnson and Kevin Hart, and Jack Lemmon and Walter Matthau, the latter of whom had a brotherly bond that lasted the rest of their lives. (Everybody knows what a bromance is today, but it’s one of the words that didn’t exist 30 years ago.)

Not all memorable motion picture pairings are between actors. Among the more notable collaborations between director and actor are John Ford and John Wayne, Martin Scorsese and Robert De Niro, and Tim Burton and Johnny Depp.