With only two league wins all season Grimsby have already this season put out League One opposition in Huddersfield, Doncaster and now Carlisle in cup competitions.
The truth was they should have won this match at the first time of asking and were more emphatic winners in the replay than the scoreline suggests.
Twice in the first half strikers Danny North and Gary Jones hit the post and they could have been comfortably ahead by half-time.
The first half was open end to end and exciting but the second period opened slowly.
But Grimsby gradually got the taste for it again and scored a marvellous match-winning goal on 61 minutes.
Jones played a lovely one-two with his strike partner, North, before producing a shot with the outside of his foot which flew past keeper Keiren Westwood and just under the bar.
This was no more than Grimsby deserved and, although Carlisle tried desperately to get back into the game, they created little to disturb reserve keeper Gary Montgomery, who did a fine job deputising for Phil Barnes who was ill.
Montgomery handled the ball superbly all night as did his opposite number and produced a magnificent save 11 minutes from time when a Danny Livesey header from a corner was heading for the top corner before the keeper turned it over.
As Carlisle took chances in their bid for an equaliser, Grimsby could have wrapped things up with North, Jones and sub Andy Taylor all going close.
There was some anxiety towards full-time given that this was their 21st match of the season and remarkably, Grimsby's first clean sheet.