Fun place, great food in Barcelona
I'd go to Cal Pep and if you go before 8:20, you can get in without standing on line. They don't take reservations. You sit at the long counter, look at what everyone is eating and start pointing. They'll put a huge bottle of Cava in front of you and charge you for what you drink. It was so great, we went back the next night.
Maybe more agreeable after a transatlantic flight than the high end food temples is
L'OLIVE,C. Balmes 47, Tel. +34-93.452 19 90, Reservation recommended (shortterm).
Genuine traditional Catalan kitchen, especially bacalao (cod fish)dishes but many others to choose, nice ambiente at reasonable prices ( 80 to 100 for two with a bottle of standard wine).
PS. MOO may serve good food but I definitely wouldn't call it a fun place.