I was wondering whether there was either a documentary or book that explains who came up with the idea to make Michelle and Joey have a lot in common? If so, any mention of the gag being inspired by classic sitcoms? It's very fitting with the characters' friendship, although the similarities are kind of subtle and are sometimes a season or more apart. It appears to have started season 3.

Examples: Both Michelle and Joey had imaginary friends; both had evil twins; both like comedy and have done impersonations; there were times when neither of them wanted to change diapers.

another thing they have in common is that they both sucked and ruined every scene that they were in.