This page explains in detail the interactions between the Conker series and the Donkey Kong series.
Conker's Poket Tales
June 08, 1999
Donkey Kong Country music in Conker's Poket Tales
Conker
Donkey Kong
As a little easter egg, if Conker stands still for a while, Conker will bring out a Game Boy and start playing. The music coming from it can clearly be recognised as an arrangement of the "Bonus Room Blitz" track from Donkey Kong Country. This works in both the Game Boy and Game Boy Color versions of the game, since they use the same sound files.
This was replaced in Conker's Bad Fur Day by a Killer Instinct reference.
License
Conker's Poket Tales was developed by Rare, that also developed Donkey Kong Country, so they included a reference to their previous work. It's unknown if Rare actually had the right to use elements from Donkey Kong, since its copyright are only held by Nintendo, but they probably didn't need it for such a minor reference.
