The text appears to be a reference to a common phrase from the television series Star Trek, where the character Dr. McCoy often declares someone dead. The humor arises from the unexpected addition of 'I'll get his wallet,' which is not part of the original phrase and suggests a humorous and inappropriate action following a death. However, it does not rely on the different meanings of a single word or similar-sounding words.
He ' s dead Jim . Grab his tricorder . I ' ll get his wallet .