Cosmo

Cosmo is an character who debuted in the Season 4 episode, "Bowser Junior's Birthday Bash".

Series:

 * Season 1 - None
 * Season 2 - None
 * Season 3 - None
 * Season 4 - Bowser Junior's Birthday Bash (debut)
 * Season 5 - None
 * Season 6 - None
 * Season 7 - New Years, We're Heres! and The Retirement

Specials:
2020: It is unknown whether or not he will appear in "The Case of the Kidnapped Princess".
 * Plushy Town: The Movie

Personality
The information is currently unknown.

Voice (compared to Joseph's)
His voice seems to sound like Joseph, except Cosmo's voice is a lot higher (and a lot louder) than Joseph. However, starting in Season 7, his voice will have to be deeper than Joseph's, because True is going through puberty.