What do you call a champagne and grand mariner?

There's no specific, widely recognized name for a champagne and Grand Marnier cocktail. You could simply call it a "Champagne Grand Marnier" or "Grand Marnier Champagne".

Here are some other ways to describe it, depending on the proportions and presentation:

* Champagne Cocktail with Grand Marnier: If the Grand Marnier is a smaller addition, like a splash or a dash.

* Grand Marnier Royale: This name is sometimes used for a cocktail with champagne and Grand Marnier, but it's not universally accepted.

* Champagne and Grand Marnier: This is a straightforward and descriptive name.

Ultimately, the best way to name it depends on the specific context and how you want to present it.