VIDEO: Boyz II Men sing about slaps on 'How I Met Your Mother'

Philly's own crooning '90s boy/man band Boyz II Men made a cameo appearance on the third installment of How I Met Your Mother's long-running "Slapsgiving" gag.

In case you're not familiar with the storied tradition of Slapsgiving, it's basically just that Neil Patrick Harris' character lost a bet, allowing Jason Segel's character to slap him in the face five times between the culmination of the bet and the end of eternity. For Thanksgiving, one year, Segel's character tortured his friend with a countdown to an epic slap that occurred during Thanksgiving dinner. Ipso facto, Slapsgiving.

On Monday night, How I Met Your Mother's final season offered another slap episode, this time with Segel's Marshall tormenting NPH's Barney by trotting out Boyz II Men to serenade him with the slap song.

Click here to watch the video.