"I always feel like an interloper when I do serious drama. It's my own paranoia"

Johnny Vegas is revealing his own insecurities about his capability to carry out in major drama. He is implying that he feels like an outsider or trespasser when he remains in a serious drama setting. This might be because he is not used to the environment or because he is not as skilled as the other stars. His own fear is preventing him from feeling comfortable and positive in his ability to carry out in serious drama. He is likely feeling intimidated by the other stars and their experience. He is also likely feeling nervous about his own performance and whether he will have the ability to deliver an effective performance. Johnny Vegas is revealing his own insecurities and fears about his capability to carry out in severe drama.