The Brisker Rov used to davka eat kneidlach on 1st night Pesach just to show the chassidim that their ‘chumrah’ is nothing more than a bobbe maisa.
The seifer Minchas Yehudah brings a maisa that R’Chaim Valozhoner once went to visit the Gaon on chol hamoed to see if he ate kneidlach, so the Gaon picked up a kneidel and ate it right in front of him and said that theres no chashash.