"It's the difficulty we had with Mr. Bean, actually, when it went from TV to film. You certainly discover that you need to explain more about a character"

Rowan Atkinson is referring to the trouble of transitioning the character of Mr. Bean from tv to film. He is suggesting that when a character is adjusted from one medium to another, more description is needed in order to make the character relatable to the audience. This is due to the fact that the audience may not recognize with the character from the initial medium, therefore more information needs to be offered in order to make the character understandable. This might include offering more background information, or more information about the character's character and motivations. By providing this extra information, the audience can better comprehend the character and become more bought the story.