It was boy band flashback week on "Dancing with the Stars" this week -- because last night the show followed up its Hanson appearance with a performance by New Kids on the Block and the Backstreet Boys!

The two groups sang their single "Don't Turn Out the Lights" and later appeared separately to sing their old school hits "I Want It That Way" and "Step by Step" -- with Joey McIntyre and Donnie Wahlberg from NKOTB showing off some moves with two of the professional dancers.

NKOTB and BSB hit the road together on tour next month.

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