"Mr Clever" was the self-proclaimed moniker of a Cyber-Planner that tried to overtake the Eleventh Doctor's mind in an attempt to resurrect the Cybermen.
It was created when the Eleventh Doctor was infected by Webley. Unlike most Cybermen, it displayed a distinct personality and emotional responses, likely due to being influenced by the Doctor's formidable persona. This could be seen manifesting in the occasional use of such phrases as "Allons-y" or "Fantastic!", such being often used by the Doctor's previous regenerations, as well as its decision to name itself and the choice of name.
It was also capable of controlling parts of the body, such as the Doctor's left arm. Mr Clever also shared the slightly manic attitude of the Doctor; leaping on tables and twirling on the spot when excited.
Although it was able to take over nearly half of the Doctor's mind, the Doctor retained the other half of it; with a small percentage of his mind unclaimed by either. The two then decided to play a game of chess, while also attempting to lead their respective allies to victory in the physical world.
Mr Clever was shown to have his own distinct personality. Mr Clever was extremely excited to discover the Doctor was a Time Lord. He was quite arrogant, not even considering the potential of losing, absolutely resolute that there was no way he could lose. He was ruthless and lacked any sense of honour, intending to go back on his agreement with the Doctor and kill everyone anyway.
Mr Clever was eventually defeated when the Doctor distracted it by claiming to have a way to avoid defeat in chess, and then removing it from his brain with a modified hand pulse. Mr Clever was then redistributed within the Cyberiad and was presumably destroyed when Hedgewick's World was imploded by command of Emperor Ludens Nimrod Kendrick Cord Longstaff XLI. (TV: Nightmare in Silver)