Simplify the following text for a Grade 7 native English-speaking person.
Original: Conan O'Brien 's Chuck Norris jokes on Late Night with Conan O'Brien ( which generally center on Walker , Texas Ranger ) have been seen as an inspiration for the fad .
Simplified: Conan O'Brien 's Chuck Norris jokes on Late Night with Conan O'Brien have been seen as a cause for the fad .