My first post aaah!
For those of you who don't know Pentatonix, they are an amazing and beautiful a cappella group of 5 people that won the Sing Off back in 2011. The members: Mitch (tenor), Scott (baritone), Kirstie (Mezzo-soprano), Avi (bass), and Kevin (beatboxer).
There was an interview with the group, and it just so happened that Kevin sneezed during it!
The build up is around 2:24 (I just love how Scott says "bless you" to Kevin too! 
)