Valerie and Yoshi ended up on the N64 version of Yoshi's Island.
"Oh wow! I remember this place from the first game!"
"Yoshi? Hmmm…" The dinosaur was looking at the back of her hands. Valerie followed his (she presumed it was a he) gaze. On the back of her hands was a Smash Bros. emblem.
John and Mario were transported to, if John knew his Smash Bros well, what he might recognize as the beginning of the Mushroom Kingdom stage from Melee's Adventure Mode.
Derek and Link would find themselves in the beginning of the Legend of Zelda stage from Melee's Adventure Mode.