Hayden's Bash Has Cake for Paps!

Geekdom's favorite cheerleader had a "Heroes"-packed fiesta last night at the LG House in Malibu -- with co-stars Milo Ventimiglia, Adrian Pasdar and Dixie Chick wife Natalie Maines, Zachary Quinto, Leonard Roberts and just added cutie Kristen Bell. Celebuspawn Rumer Willis and Hayden's random family friend Mario Lopez were also spotted leaving the party.

'80s songs and hip-hop were the music of choice at the bash, but the festivities weren't limited to just inside the house -- Panettiere even had an assistant bring out red velvet cake to all the paparazzi waiting outside!