pack them in - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Attract a large audience, as in A big star will always pack them in. This idiom alludes to tightly filling a hall. [c. 1940]