[2] Fill taken from the cut to build the MacArthur Tunnel was dumped near Mountain Lake during the construction of the Funston Avenue approach to the Golden Gate Bridge in 1939.

[4] The lake also became a dumping ground for unwanted pets, including crawdads, large-mouth bass, goldfish, carp, bullfrogs, turtles, and even an alligator, which was discovered and removed in 1996.

In October 1996, a male alligator, 3 feet 2 inches (0.97 m) in length, was removed from Mountain Lake by San Francisco Zoo associate curator John Aikin.

[13] Long, a licensed alligator control agent, brought his own gator lures and gear, including a fishing pole and line with a triple hook.

[13][7] While at the Zoo during the second day to strategize, Long mentioned that he had never been to a major league baseball game, which was misreported by a local television station that he was at a ballgame while the alligator made an unexpected appearance in the lake.

[16] As he was returning home, Long, who had previously toured local sights during his stay, expressed appreciation, regret, and confusion saying "San Francisco is the most beautiful city in the world.

"[17] KBAE, a radio station in Horseshoe Bay, Texas broadcast frequent updates on the alligator and one of the listeners, Shelli Spruiell, wrote new lyrics to Elton John's song "Crocodile Rock" in homage.

[6][18] Worried the cold weather might spell the creature's doom,[7] the Examiner reassured readers that as long as it truly was an alligator, not a caiman, it would survive the winter in San Francisco.

[19] Both the Chronicle and Examiner were criticized for drumming up too much publicity, which made catching the alligator more difficult, and for wasting resources on covering a relatively unimportant story.

[10] After his removal from Mountain Lake, Golden Gator was temporarily housed at the San Francisco Zoo in a heated pond,[9] converted from a monkey cage in the primate center,[20] where he was measured and sexed.

A local transient claimed to have moved Myrtle from the Palace of Fine Arts in the Marina District to Mountain Lake Park after seeing her being harassed by a group of young men.

[23] Myrtle was transported from the park to the Zoo in February 1992 to convalesce from an apparent bite wound on the neck, possibly caused by dogs or raccoons.

[23] While visibly ill in June 1997, Myrtle was again removed from the park to the Zoo without incident, and she was subsequently treated for lead poisoning and a fungal infection in her lungs.

There is a cinder block structure opposite the 9th Avenue entrance known by neighbors as the "card shack", which has picnic tables and is a popular location for birthday and neighborhood parties.

At the eastern end of Mountain Lake Park, inside 8th Avenue, is an area set aside for owners to take their dogs off leash for exercise and socialization.