in USA,most universities have sport teams and have what we call "Mascots" which could be animals or fictional figures.Mascots become some types of symbols for that particular schools.During sport games,an actual human being would wear a set of costume of that animal (similar to those worn in Disney) as part of the cheerleading team.I am not sure if that term applies to disney,but in general,the word "mascot" becomes a commonly-accepted term to refer to such costume.