Yep, TE RA TA GUU (so it's not a tsu, it's the elongation symbol)
thanks Gaki! tell your friend that it's cool but absolutely nobody, not even a few people that came into the shop that know Japanese, got it I suppose they weren't allowed to have their name on the tshirt at all. I guess that the person that cleared the design on the movie company end didn't know their katakana to see that it's not anything to do with the movie