Determine what type of music your skit calls for. Are you planning a mascot dance or a cheer to get the crowd going? The right music choice depends on your mascot character, the amount of time you have for your skit and any additional props you require. For a rally dance, consider music that will get the crowd pumped up. However, if your skit calls for a very specific genre of music, go with that instead.
Add additional songs to your skit as you see fit. Perhaps your character will begin with a rambunctious routine but will then get sad and then will get rambunctious again once the crowd cheers. For this, you will want multiple music selections mixed together. Create a mix as a playlist in iTunes. Once you think you have all the songs that will fit your skit, practice with a run-through to make sure your routine matches up to the song or songs you choose.
Put your song or playlist onto a CD or MP3 device. Based on the size of your audience, you may wish to hook up the device to speakers or use a CD player. Get a friend to help you and press play at the necessary time. For best results, test the speaker's volume and any equalizer (e.g. bass or treble) options before the crowd arrives. This will help you determine if the mix needs additional volume or changes to its equalization.
Give your device or CD to a sound operator if your routine will take place in a larger setting such as a stadium. Talk to the sound operator before the show and see if she will grant you a trial run. This will help you ascertain the overall mix of the music in a large setting. Work with the sound operator to adjust volume and equalization to match your mascot performance space.