Most pet cats will become timid or defensive when outdoors, but not Millie – after being adopted by her mountain-climbing owner Craig Armstrong, Millie has become a feline hiking and mountain-climbing legend.

People wait on a taxi line near Madison Square Garden, Wednesday, September 23, 2015, as a 225-foot-tall hand-painted billboard of Pope Francis stands out at Eighth Avenue in New York. The billboard, designed by Israel Ochoa of DeSales Media, including a photo by photographer Giulio Napolitano, marks the arrival of the pope Thursday. (Photo by Craig Ruttle/AP Photo)

Hundreds of people pack the Canaveral national seashore's Playalinda Beach as a United Launch Alliance Atlas V rocket, carrying a U.S. Navy communications satellite, lifts off from Complex 41 at the Cape Canaveral Air Force Station, Friday, June 24, 2016, in Cape Canaveral, Fla. The satellite is designed to significantly improve ground communications for U.S. forces on the move. (Photo by Craig Rubadoux/Florida Today via AP Photo)

Advanced Space Suit Engineer at NASA Kristine Davis wears the xEMU prototype space suit for the next astronaut to the moon by 2024, during its presentation at NASA headquarters in Washington, U.S., October 15, 2019. (Photo by Carlos Jasso/Reuters)

USA's Tara Davis-Woodhall reacts as she competes in the women's long jump final during the World Athletics Championships at the National Athletics Centre in Budapest on August 20, 2023.. (Photo by Marton Monus/Reuters)

Internet personality Brock Davies and American TV personality Scheana Shay attend the 2024 People's Choice Awards at Barker Hangar on February 18, 2024 in Santa Monica, California. (Photo by AFF-USA.com/The Mega Agency)

Tara Davis-Woodhall, of the United States, reacts after an attempt in the women's long jump during the World Athletics Indoor Championships at the Emirates Arena in Glasgow, Scotland, Sunday, March 3, 2024. (Photo by Bernat Armangue/AP Photo)

Tom Lishness of Windsor, who has been competing in the event since 2005, gets into position for the Damariscotta Pumpkinfest & Regatta on Monday morning, Oct. 14, 2024, in Damariscotta, Maine. (Photo by Derek Davis/Portland Press Herald via AP Photo)