When Ted goes to the karaoke bar, he sits down to talk to Marshall. Barney is heard singing "Dirty Deeds Done Dirt Cheap" by AC/DC in the background while Ted and Marshall are talking.
However, at points in their conversation, Barney can be heard singing into the microphone when he is actually dancing with the microphone nowhere near his mouth. See more
[after telling Lily how he wants to provide them with the 'life ideal' of home, school for the children, et al
I know that you don't need it, but I love you and I want to give it to you anyway. I want to give you the package.
The package? You've already given me the package. You've got a great package, Marshall. I love your package.
Lily, you're the most incredible woman I know, and you deserve a big package.
Your package has always been big enough. You may not realize this Marshall Eriksen, ...