"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 difficulty of transitioning the character of Mr. Bean from television to film. He is suggesting that when a character is adapted from one medium to another, more explanation is needed in order to make the character relatable to the audience. This is because the audience may not be familiar with the character from the original medium, and so more information needs to be provided in order to make the character understandable. This could include providing more background information, or more details about the character's personality and motivations. By providing this extra information, the audience can better understand the character and become more invested in the story.