The chef has to be a stoner to think celery and lettuce would be good for sushi. Cream cheese is sacrilege enough as it is, but at least it's a staple for the crowd who thinks water is too spicy. Celery and lettuce sound like a disaster in a sushi roll.
In all honesty, it's the celery that really throws me off from this whole thing. Lettuce can work on those trendy rice paper rolls (not sushi, mind you, but they sell it on that menu anyway), but there isn't a universe or alternate universe where celery on sushi doesn't sound disgusting.