It's in season 8 episode 3 of How I Met Your Mother at 8:22min. I found it on youtube too.
"Barney!!!" "Icksnay on the ealray amenay!" "Mr and Mrs Erikson?" "Youuu son of a... itchbay!"
The itch-Bay was easy. And to me the previos is: Nicks on the real name! But what does that mean? A referrence to the NY nicks? I don't get it.