Donald Trump is remembering Arnold Palmer for something other than golf or a refreshing beverage ... his huge penis.
The presidential candidate couldn't stop talking about Arnold's manhood over the weekend during a campaign rally in Palmer's hometown of Latrobe, PA ... claiming the golf legend was hung like a horse.
So naturally, we talked about it today on "TMZ on TV" ... and Trump's story about Arnold in the shower came as news to all of us.
Of course, not everyone is buying it ... but we're guessing Arnold wouldn't object to Trump's penis praise.