Holy mackerel

[Rihanna]

[Holy mackerel] is an expression of surprise, astonishment, joy, glee, incrudulity.
Holy mackerel is an ejaculatory term - meaning it occurs rather sudden.
The meaning of the name is an oxymoron, as the [mackerel] (Atlantic mackerel) is one of the smellier fish and juxtaposed against the Holy, there is nothing Holy about that smell. So in other words its a bit ironic and thus is funny to hear.
[Holy Mackerel], Batman is a fav culture classic from the 1960s TV series show Batman that starred Adam West and Burt Ward.

[Vania]

used to show that you think something is surprising, shocking, or impressive: