No video footage survived of the Slamfest '99 Super Smash Bros

The year was 1999 and recording was by no means as simplified and widespread as it is today, but Nintendo's Super Smash Bros. 64 promotional event in Las Vegas was indeed recorded, in fact, it was actually broadcasted live

Super Smash Bros. - Super Mario Wiki, the Mario encyclopedia

New Photos from the Lost Super Smash Bros. Slamfest '99 Event Have Emerged : r/nonmurdermysteries

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Some arrogant moron claimed that I don't know anything about Smash so, because I'm petty, I made this to prove my knowledge of the series. This is my Super Smash Bros Iceberg!

University of Indianapolis Archaeology

Lost Smash Bros. Slamfest '99 Photos Put Pikachu, Mario, and Yoshi in a Real-Life Ring - IGN

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Super Smash Bros. - Super Mario Wiki, the Mario encyclopedia

Lost Media – Ronstar's Urban Legends