nyc justin timberlake Amanda Seyfriend southern hospitality

Justin Timberlake has been off the music scene for years, but a few lucky folks got a blast from the past in NYC on Wednesday night!

Timberlake stopped by his Southern Hospitality restaurant and gave an impromptu show!

Celeb guests include the Kardashians (see gallery below), and Justin's In Time co-star Amanda Seyfried -- check her out behind Justin in the pic above!

JT did a rendition of "What Goes Around ... Comes Around" -- wonder if he was referencing his relationship with ex Jessica Biel ... the two are reportedly back together!

See pics of the Kardashians heading to Timberlake's concert after the jump!