Mr. Smiley

Mr. Smiley; voiced by Derek Nimmo. A nutty psychiatrist, who tried Dennis like practical jokes on the parents during his course on "How to Understand Children", but couldn't get the better of Dennis even though the parents though he was worse than him. Seen in Dennis and the Grown-Ups.

Trivia

 * Mr. Smiley is truly one of the nuttiest characters in the series, even going to great lengths to turn Dad back into a menace.