Parker is a reformed criminal, having served prison sentences for and safe-cracking. His criminal exploits, coupled with a prominent facial feature, earned him the nickname "Nosey" (this may also be a reference to his nosiness – he eavesdrops on his employer's conversations in "Vault of Death" and "Thunderbird 6"). He was rescued from a life of crime by Penelope, who recruited him as an aide in her espionage activities. Parker's underworld contacts frequently prove useful during the pair's missions (such as in "The Cham-Cham", when he blackmails a talent agent to have an undercover Penelope pass off as a nightclub singer). It is revealed in "The Cham-Cham" that Parker suffers from vertigo. In the episode "The Man from MI.5" it is revealed he still has the temptation to return to his burglar ways as he was caught with a suitcase full of safecracking equipment, much to Penelope's chagrin. He later complained to himself about the situation, saying "'Ow she expects me to keep my 'and in I don't know".