I don't know if these people are really famous but they've been in very famous movies.
Polly is Julie Hagerty was Elaine in Airplane!, which AFI called a top 5 comedy movie
Otto is Kenneth Mars who played Franz on The Producers which has gone full circle from movie to hit Broadway show back to a movie and is the first and probably best work of Mel Brooks
Ida is Cloris Leachman who has been in many Mel Brooks movie including Young Frankenstein, High Anxiety, and History of the World Part I and was a supporting character on the very popular Mary Tyler Moore show.
Two characters from the Golden Girls have been on Malcolm. Betty White, who was also Mary Tyler Moore was on the Victor's Other Family episode and Bea Arthur was on the Waterpark episode.
Merrin Dungey who played Malcolm's teacher in the pilot and then Stevie's mom is a regular on two current TV series, Summerland and Alias.
Laurie Metcalf who played Lois' sister Susan was also Roseanne's sister.
Jason Alexander of Seinfeld fame and currently on Listen Up played the Chess player on Future Malcolm.
Christopher Lloyd of Back to the Future was on the Family Reunion episode.
And of course the whole slew of people on the company picnic episode most of which have already been mentioned.