Derived from the wiki:

"Glisten is a charismatic mirror who always wants the spotlight! Sometimes his ego brings up new issues but he will always stand up for his friends and what's right."

Outwardly, Glisten is a charismatic, prideful and outgoing Toon. He enjoys being the center of attention and being included by the other Toons, and is obsessed with appearing perfect in both his appearance and capabilities.

However, underneath his flamboyant persona, Glisten is rather insecure, as implied in many of his interactions, becoming defensive when they point out his shortcomings. He often overworks himself in maintaining his flawless facade.

His voice should sound something very close to Lollipop (Battle for BFDI), perhaps with a bit more variation in tone if you want.