As I just mentioned in another topic, musicstyle could give both lots of character. And the game is a heavily linked to music piece of software, so why not.
As both Yooka and Laylee share a cave alongst a very sunny side of a canyon they constantly argue about each others habits. And how the cave should be decorated.
Yooka, as a colorloving animal loves Disco music and bright lights, and has the cave littered with discobals and glitter. Laylee just hates those happy tunes and is much more into metalmusic, with much black leather, electric guitars and iron bars.
An ideal twist to argue about and its easy to provide both with much character.
Even the discussion of clothes could be tackled with this, since both could collect many music attributes linked to metal or disco.
Hell, Moomajooma could play a magical ukulele to help the duo with their relationship troubles