Ryan Reynolds is glad his first choice for Deadpool's signature song was too expensive for the movie, because the second option was much better.

The actor always envisioned Gwen Stefani's Hollaback Girl would be his character's jam, but he had to rethink his musical direction when producers informed him they couldn't afford to use the song.

Instead, he opted for Salt-N-Pepa's Shoop.

"The Shoop idea came because what we had written into the script we couldn't afford, which was Hollaback Girl by Gwen Stefani," Reynolds tells Entertainment Weekly. "We got Shoop instead because it was less expensive, but also it was so much better for the movie."

Meanwhile, Reynolds fears film fans who picked up the Deadpool DVD for Christmas may be getting a little extra - glimpses of his manhood in naked fight scenes.

"In certain shots I'm wearing a codpiece, and other shots you can't do much about it," Ryan explains. "There are flicks of Deadpool peen (penis) in there.

"If you're at home with your DVR, you can freeze-frame that!"