Sounds supicously like a Quick Fuck.

1/3 Kahlua
1/3 Midori
1/3 Bailey's

Fill your shot glass with the Kahlua first then the Midori, the slowly pour the Bailey's Irish Cream over the back of a spoon so it floats on top.

Now that looks like a real Guinness.

A warning though, these aren't quick bliss like the name suggests. They are highly addictive and the quickest way to coma.