After you've beaten Hot-Head Hop, return there with both Diddy and Dixie. When you first enter the stage, throw your partner on top of the entrance and go up. You'll find a treasure chest sitting ...
Amazon has nice deals on Diddy Kong's Mine Cart Ride and Dixie Kong's Jungle Jam from the Lego Super Mario line.
Donkey Kong Country 2: Diddy's Quest (1995) The Donkey Kong series got its first female playable character in 1995 when Dixie Kong was introduced in Donkey Kong Country 2: Diddy's Quest.