The line comes from Nickelodeon's SpongeBob SquarePants, which premiered in 1999. Mermaid Man and Barnacle Boy are Bikini Bottom's elderly, retired superhero duo, a loving parody of classic TV heroes, with Mermaid Man voiced by Ernest Borgnine. To the Invisible Boat Mobile is their signature rallying cry before they rush off to fight crime. Clips of the shout circulated on YouTube, meme pages and soundboard sites throughout the 2010s, and it endures because it instantly signals campy heroism and deep cartoon nostalgia for millennial and Gen Z audiences.