Zac Efron -- Hangin' with Nickelodeon Star During DUI

7/8/2011 2:20 PM PDT

Zac Efron -- Hangin' with Nickelodeon Star During DUI

A concerned Zac Efron was videotaped anxiously talking on his cell phone as his friend Ryan Rottman was being arrested for DUI last night ... and Bruce Willis' daughter was there too!

The new footage was posted on PopCandiesTV -- showing Zac (in a plaid shirt) pacing around Dillon's Irish Pub while LAPD officers spoke with Rottman (in the DARK blue shirt).

can be seen taking a field sobriety test around 2:00 into the video.

Rumor Willis
appears at the end of the clip -- and can be seen driving Zac Efron away from the scene. 

As TMZ first reported ... Rottman -- star of Nickelodeon's "Gigantic" -- was originally pulled over in Hollywood after his car jumped the curb. Cops detected alcohol -- and a breathalyzer showed his blood alcohol level was more than twice the legal limit.

He was taken to jail, booked and released a few hours later without having to post bail.