'50/50' preems at Ziegfeld in Gotham

The Rx for Monday night’s “50/50″ premiere at the Ziegfeld in Gotham was laughter — and lots of it.

Summit Entertainment’s dark comedy, based on writer-producer Will Reiser’s battle with cancer, gave good friend Seth Rogen a chance to imagine himself without his curly locks.

“I actually shaved my head in high school … and it wasn’t pretty. My physical appearance got much worse,” joked Rogen. “My fashion sense isn’t much better. The last thing I bought was a strap-on dildo yesterday.”

Reiser quickly came to his pal’s aid, and added, “He wears it well, though.”

Pic’s Joseph Gordon-Levitt explained that it was his second time breaking out the shears to shave his head.

“I just got done doing this really heavy movie called ‘The Lookout’ and I wanted to get out of that head space so I buzzed it,” Gordon-Levitt said of the 2007 pic. “I regretted it quickly as my head was so cold right away.”

Post-preem, guests filled the Four Seasons Restaurant for an extremely mellow party.

“Saturday Night Live” star Bill Hader overheard the shaved-head question and said to Gordon-Levitt, “C’mon, I’m sure it didn’t look that bad. I would like to do it but I have this huge dent in my head. I would look like a ‘Star Wars’ character.”

“Today” host Hoda Kotb congratulated co-stars Anjelica Huston and Anna Kendrick, who wouldn’t spill any beans on the upcoming “Twilight” installment.

Edward Norton chatted with Hader, Rogen and his fiance, Lauren Miller, over cocktails and sushi.

“Adding humor to such a sensitive subject is extremely difficult,” said Norton. “But they made it work.”

Added Hader, “The end just makes you want to smile.”

Follow @Variety on Twitter for breaking news, reviews and more