India vs England, 2014
The first test match between India and England was heading towards a draw with India scoring 385/8 with 3 overs remaining (India saved the match courtesy the tailenders like Bhuvaneshwar Kumar and Mohammad Shami). So nobody was expecting any result and to kill time Cook decide to do bowling something he has rarely done in any form of cricket.
So Cook rather than bowling with a regular bowling action started imitating the bowling action of different Bowlers, particularly imitating Bob Willis, a bowler he had imitated in the county cricket as well. Commentators started guessing which bowler is he going to imitate now. Even tha batsman Ishant Sharma was enjoying the process.
And then suddenly he nicked a ball on the leg side and it was taken by Matt Prior. And jokingly Cook got his first and only Test wicket!! The match ended in a draw with Shami hitting a four off Cook. With this Cook ended his bowling career with one wicket in 3 overs (he had bowled 1 over in 2008) and with an economy rate of 2.33 which is impressive. Wish he had bowled more.