Debbie Wolowitz

Mrs. Wolowitz is the mother of Howard Wolowitz and the mother-in-law of Bernadette Rostenkowski Wolowitz (as of The Countdown Reflection). As a joke in the series, she never appears on screen, albeit a single above shot of her on the roof of Leonard and Sheldon's apartment building during the the episode The Countdown Reflection when she is attending Howard and Bernadette's wedding. Her portrayal is limited in the series to her loud and obnoxious voice that originates from off-screen or through electronic devices.

Physical Description
Mrs. Wolowitz's physical description is limited to clues given by the characters who have interacted with her.

Verbal descriptions depict her as an immensely overweight woman with a mustache, as she takes water aerobics classes for overweight people. She once mentioned that she was a beautiful woman of whom the boys used to flock to, receiving candy from them. Clues to her appearance have been mentioned in several episodes, including in the episode The Hot Troll Deviation, in which she states that she was spilling out of her shrunken girdle like "The Pillsbury doughboy". In the episode The Hawking Excitation, Sheldon states that he strained his wrist while helping Mrs. Wolowitz lift her "bossom" when he takes her dress shopping, further confirming her excessive weight. Another more prevalent mention of her size was in the episode The Engagement Reaction, in which Penny doubts Howard's ability when he stated that he lifted his mother up to take her to the hospital. Penny's doubt was founded in the belief that Mrs. Wolowitz's own legs were barely able to lift her up, never mind her petitely built son.

In the flashback episode The Staircase Implementation, Mrs. Wolowitz had a younger, even louder and a very masculine voice, that makes Leonard mistake her for Howard's father. Howard promptly points out that with any more facial hair, she could pass off as his dad.

History in the series
Mrs. Wolowitz was abandoned by Howard's father when her son was 11, before then, they just stayed together in silence without saying a word or being drunk all the time, as mentioned in The Grasshopper Experiment. Howard lives with her and often refers to her as "living with him", even though its obvious that she's the responsible one when it comes to living standards.

Mrs. Wolowitz often talks to her son like he is still a child and isn't aware of his adult accomplishments, filling the cliche of a Jewish mother, referring to his colleagues and friends as "playmates" or "little friends", and refering as his work at the university as "going to school".

Howard often makes references to his mother as being a "crazy old lady", but deep down, he is still attached to his mother, being such a Mama's Boy. The attachment is primordial, as he relies on her to wash his clothes, as well as alimentary needs. Howard has no problems with this, as he gets to keep eating his old-time favorite childhood foods.

Her cooking skills are mixed. She is able to cook a brisket to the point where it just melts in the mouth. But she takes things beyond edible on Thanksgiving with her "tur-brisk-efil" (which is turkey stuffed with brisket stuffed with gefilte fish). Also, her meatloaf lacks breadcrumbs and has been used over the generations to test diverse plumbing systems, including Howard's famous "space toilet".

Howard's mother is rigorously Jewish. She evaluates Howard's partner choices vociferously (like insisting that the latter be Jewish too), but she does not take kindly to strangers taking control inside her house (as in her argument with Howard's partner, Christy in The Dumpling Paradox). Despite this, she stated in The Engagement Reaction that she likes Bernadette, even though Bernadette is not Jewish, considering she went to Catholic School. Bernadette has developed some of the same personality quirks as Howard's mother including shouting like her when upset and mothering her husband.

Communication with other characters
Mrs. Wolowitz usually shouts at whoever she is talking to, but on occasions has been heard to speak in a softer tone. This is particularly true in the episode The Hawking Excitation when Sheldon takes her shopping for a dress and she asks him to "hold" her after Sheldon makes a comment about her inability to fit into a dress. Whenever she speaks, she is usually heard either shouting from another room, off-screen, or over the phone.

Trivia

 * She regularly goes to the gym and eats Oreos while in baths.
 * She is extremely good at figuring out the answers with only sparce clues on the gameshow Wheel of Fortune.
 * Carol Ann Susi has said that Chuck Lorre has decided to never show Mrs. Wolowitz onscreen.