I did not know about that finger crossing thing. Never saw it before in sushiyasans. Usually customers say - oaiso, which means bill me!
Well the video is a comedy so I guess they're taking the mickey out of Americans and Brits that do the whole finger crossing thing! I didn't know the phrase oaiso before though - I usually just use okanjou wo onegaishimasu which is the expression I was taught. Is oaiso more natural?