Born at the Dublin Zoo[4] on March 20, 1919, and originally named Cairbre[5] (Irish for 'charioteer'[6]), Slats was used on all black-and-white MGM films between 1924 and 1928.

Later, Phifer planted a pine tree directly above the grave so that the roots would "hold down the lions spirit", replacing the granite block.

Jackie appeared on all black-and-white MGM films from 1928 to 1956 (replacing Slats), as well as the sepia-tinted opening credits of The Wizard of Oz (1939).

Two films directed by William A. Wellman, Westward the Women and The Next Voice You Hear... (both 1950), used a still frame of the logo – sans growling— at the beginning.

It was once rumored his body was flown to Los Angeles and preserved by a taxidermist named Thomas Hodges and then sent to McPherson, Kansas.

He is known to have appeared in the silent color films Buffalo Bill's Last Fight (1927) and The Heart of General Robert E. Lee (1928).

Like Jackie, Tanner[3] was trained by Mel Koontz and appeared on all Technicolor MGM films (1934–1956) and cartoons (1935–1958, 1963–1967, except for 1965's The Dot and the Line), replacing Telly and Coffee.

The Picture of Dorian Gray and The Secret Garden, released in 1945 and 1949 respectively, both had brief color sequences, but were otherwise in black-and-white including their opening credits, so they used Jackie instead of Tanner as well.

For Ben-Hur, the reason for this was because the film's director, William Wyler, thought that the roar would feel out of place for the opening nativity scene.

The usual film ribbon appeared on-screen with the sound of Leo roaring and the phrase "BEGINNING OUR NEXT 50 YEARS..." on a black background within the film circle; the phrase dissolves as "Metro-Goldwyn-Mayer" (above the ribbon) and "GOLDEN ANNIVERSARY" (in place of the usual "TRADE MARK") both rendered in gold fade in along with Leo, who continues to roar.

It was also at this time that the original lion roar sound (which, in fact, sampled Tanner's roar) was replaced with a remade stereophonic one, redone by Mark Mangini (and made of tiger sounds; as Mangini would later explain, "Lions don't make that kind of ferocious noises, and the logo needed to be ferocious and majestic.").

Shine Studio re-built all the elements of the logo in 3D and then placed on different planes to add dimensional layers and drama, including the words "Ars Gratia Artis" moving from right to left.

On March 8, 2021, MGM unveiled an updated logo, with Leo now being CGI-animated, while being based on its 1957 footage, the first major re-design for the mascot in over six decades.

The latest rendition leans into the company's traditional gold design, filtering out sepia tones and modernizing the logo by sharpening the film roll, mask and lettering.

It premiered in front of the IMAX re-release engagement of No Time to Die on January 21, 2022, and appeared on Ron Howard's Thirteen Lives and the documentary The Sound of 007.

This version premiered on the teaser trailer for Saltburn and made its official debut on Sitting in Bars with Cake, which was released on Prime Video on September 8, 2023.

A refined version of the stylized lion is currently used as the logo for their parent company, MGM Resorts International, no longer affiliated with Metro-Goldwyn-Mayer.

The logo features a graphic image of a reclining lion (from a side view) on a pedestal with a banner below it and the text "A Metro-Goldwyn-Mayer Picture".

Many of the short subjects produced by Hal Roach studios and distributed by MGM during the late 1920s and 1930s such as Our Gang and Laurel and Hardy featured a variation of the secondary logo in their closing titles.

In addition, several MGM films made in the late 1930s and early '40s set their opening credits against a background of a relief carving of an outline of the reclining lion image, similar to the one seen on the secondary logo.

Among the many films that include this kind of credits sequence are Ninotchka (1939), starring Greta Garbo and This Man's Navy (1945) with Wallace Beery.

In the second episode, he reclines on a bookcase in the "MGM Trophy Room" set, wearing full evening dress (but no shoes).

Motion Picture Daily's coverage of Jean Harlow's sudden death (on June 7, 1937) includes full page artwork on page 2 of the June 9, 1937 issue showing a lion, dressed in evening clothes and holding a mourning wreath, standing head bowed before a photograph of Harlow.

The UK TV series The Goodies episodes "Gender Education" and "The Movies" parodied the logo with a blanket obscured man and a chicken respectively taking the lion's place.

MGM's compilation film The Big Parade of Comedy (1964) opens with Leo "out to lunch" behind a pulled down shade, munching on an animated protestor.

The 1983 comedy film Strange Brew opens with a one-off version of the MGM logo where the inebriated lion belches after the fade-in.

In the 2014 film Robocop, the lion's roars are changed with the sound of talk show host Pat Novak doing his vocal warmups.

In The Pink Panther (2006), starring Steve Martin, Leo starts roaring, but is then interrupted as Inspector Clouseau opens the circle like a door, looking around the place before leaving.

The Pink Panther character appears behind him unnoticed, cleverly smirking, and closes the door immediately afterwards, leaving Leo confused.

One of the end tags and post-credit scenes featured the character Furrball, who began by roaring at the screen like a lion before covering his mouth and letting out an apologetic mew.