[onedoug]

‘You say Denali,
And I say McKinley.
You say potato,
And I say potahto.
McKinley.
Denali.
McKinley.
Denali.
Let’s call the whole thing off.’

[Zhang Fei]

And I say potahto.

No one actually pronounces it potahto. It's a line of whimsical gibberish from a Gershwin song. Banahna and tomahto, yes. Potahto, no.