Molly is the local nightclub and bar for mountain view locals. Thursday night is the happening night at Mollys when all the skanks in San Jose and the penninsula come to Molly's and party. There is a $5 cover charge only on Thursday nights, where they bring in a DJ and hundreds of people party the night way until Molly closes at 2 am.
Other nights, Molly is more low key and definately not crowded. It is a normal bar every other night, and I've never seen it filled with more than 30 people on a non-Thursday night.
Parking gets hairy on Thursday night, you may have to park several blocks away on the street.