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

Slamfest '99 aka Super Smash Bros. LIVE (lost livestream of promotional event for Nintendo 64 crossover fighting game; 1999) - The Lost Media Wiki

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Slamfest '99 aka Super Smash Bros. LIVE (lost livestream of promotional event for Nintendo 64 crossover fighting game; 1999) - The Lost Media Wiki

The Road Theatre: Under Construction – New Play SLAMFEST 3

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New photos from the lost Super Smash Bros. Slamfest '99 event have been uncovered! : r/retrogaming

Slamfest '99 aka Super Smash Bros. LIVE (lost livestream of promotional event for Nintendo 64 crossover fighting game; 1999) - The Lost Media Wiki

Sandy Cheeks, Universe of Smash Bros Lawl Wiki

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

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Searching for Slamfest '99 - The Lost Nintendo Event (Update)