For older members, these videos need no explanation. For younger members, they might. In the mid 1990's Nintendo Power started sending out promotional tapes to subscribers to their magazine (and non-subscribers who'd officially registered their systems). These videos were notorious for their lame acting and low production values.
Enjoy the ones I've found, and if you can find more, post 'em.
Donkey Kong Country: Exposed!! (watch until the end for their Killer Instinct Preview)
There are Things You Can Only Do on Nintendo 64 Star Fox 64 Pokemon:
Part 1 Part 2 Banjo Kazooie Diddy Kong Racing