The meow sample is in the song already (the drums and some of the guitar and bass are being done live) and meesh was already on stage for another song so they had her do the meows too (on top of the samples already in the song).
@@Mergatroid Meesh's own talents and endeavours aside, just the thought of someone actually shouting "meow" for a performance of this song tickles me so much. It's already silly enough with "meow" being the only "lyric" in sampled form. I love sharing this vid with people to make them go "WTF?!"