Lip-synching skits are pretty much a no-no. They get boring and very awkward. I would recommend writing a skit with your own dialogue. It's more work, but the audience and judges will appreciate it a lot more.
Anime Midwest cosplay: Armin + young Armin Arlert (Attack on Titan), Madoka Kaname (Madoka Magica), Mayoi Hachikuji (Bakemonogatari)