but seriously

This term is usually used after saying a non-intended humorous quote or phrase.

This term can also be used to put a serious twist on your joke, and frequently intensifies the situation.

It is also used to make a joke more humorous, this is called backing-up(usually used after your not-so-funny-joke)

#1:
Person 1: Yeh i got a vest the other day!
Group: HaHahahAhAh
Person 1: but seriously

#2:
Person 1: I've got a vest....jokes....but seriously
Group: HaHahahAhAh

#3:
Person 1: Vest are only for 'homos'
Group: *cough*
Person 1: but seriously!
Group: HaHahahAhAh

by Semaj R. Llih and Samoht H. Nosreme February 20, 2007