Conversation so far:
Where did Anthony McPartlin begin his career?
McPartlin's first appearance on television was on the children's workshop programme Why Don't You?
Was the show Why Don't You? the only show Anthony McPartlin was on?
His big break came when he rose to prominence playing the character of PJ in the CBBC series Byker Grove.
Why was the show Byker Grove important to Anthony McPartlin's career?
It was during his time on the programme that he first met Declan Donnelly, who was cast in the part of Duncan. The pair formed a close friendship.

Question: What was a hallmark of his career?
Self-contained rewrite: What was a hallmark of Anthony McPartlin's career?