Continuity mistake: During "I Should Tell You" Roger and Mimi are walking out in the snow. As they walk away from The Life Cafe you can see their footprints in the snow. When they turn to walk back toward the cafe all of their footprints are gone - they are now walking on a fresh blanket of snow.
Continuity mistake: When everyone goes into the diner the entrance/exit is on the left side, but then Roger and Mimi leave on a different side of the building and then come back in on the same side they left originally.
Continuity mistake: When Mark and Roger sing the lines, "You're wasting your time, we're broke. And you broke your word, this is absurd." None of the burning papers from the song "Rent" can be seen on the sidewalk. But before and after this portion of the song, they are visible.
Answer: "This egg needs some salt." It's a Spanish idiom meaning that he needs a girlfriend.