A Mouse in the House is the 32nd cartoon of Tom and Jerry that was made in 1947.
A fed up Mammy Two Shoes threatens to rid of one of her lazy cats when she's tired of dealing with all the mice problems. However, both cats as well as Jerry are out of the house in the ending.
Mammy Two Shoes enters the kitchen which has been ransacked by Jerry, and goes on a tirade against the residents of the house: Tom and Butch. She goes into the living room, where she finds them lazing around and drinking cream. Sarcastically pleased that the cats are satisfied, she yells at them about the mouse in the house and whoever catches the mouse stays in the house.
The two cats frantically begin their search for the mouse, and are unsuspectingly aided by Jerry before realizing the mouse was under their noses the whole time. In an attempt to catch him they become entangled. On only one of their four feet, they tiptoe across the floor until the mouse motions at them to stop and hits that foot with a fireplace log. This was Butch's left foot; he screams, jumping up and down, clutching Tom's left foot and eventually noticing he's got the wrong foot. He lets go of Tom's foot and grabs his foot, screaming appropriately.
Tom and Butch both grab Jerry together and decide to have a duel using a pair of guns they find lying around. Tom turns around early and shoots Butch as he turns around, but Tom finds out he is holding a "novelty gun", which whacks Butch on the nose. Butch (who thinks he has a real gun) angrily chases Tom into the wall, but when Tom sees exactly the same brand name on it, he assumes it is another novelty gun, chuckles at this and snaps his fingers in victory. Extremely angry at this turn of events, Butch proceeds to shoot Tom; the gun goes off, and Tom has barely dodged the bullet, but it comes out of the wall, rolls down Tom's head and onto his nose.
Tom threatens Butch in order to give him Jerry and the chase continues in the kitchen, where Jerry jumps into the oven. Tom and Butch slam the door and turn on the gas as Jerry sneaks out, lights a match and drops it in the oven. Tom and Butch open the oven door, puzzled as to wondering why the oven hasn't exploded yet...and then it does, leaving them in blackface.
Jerry and the cats move into the living room, and the two cats hide to catch the mouse by stealth. The mouse looks both ways, slowly walks out, and is caught by both cats simultaneously. Jerry squeezes out of their grip, but is then grabbed by Butch. Tom grabs his opponent's tail as he flees, keeping the cat from running away, but provokes further attacks: Tom bops Butch on the head, and Butch slips the mouse into a box with a sliding cover before continuing the fight.
Jerry escapes from the box and rings a boxing gong, ending the fight, and cleans up and coaches both cats to hit each other. Jerry rings the gong and both cats end up punching each other, as planned. They realize they've been tricked and glance towards Jerry, who is making fun of them by punching the air. Both of them pull up on either side of the mouse, incensed at the idea of a mouse tricking them into bopping each other. Eventually seeing he is trapped between the two and thus also realizing that he pushed them around too far, the mouse chooses Butch via Eeny Meeny Mine Mo, makes a face to Tom, and sits down in Butch's hand.
Butch assumes that he has Jerry in his clutches and dares Tom to walk out in the morning. Tom slumps down and walks away, then hides behind a curtain. Butch is reveling in his victory until Tom reaches out and grabs Jerry directly out of the other cat's hand. Butch turns the corner and opens the curtain to find only Tom, who pretends to not know where the mouse is; in reality, he is underneath the cat, who lifts Tom up and carries him around to reveal himself. Tom simply continues with the charade, and Butch grabs Tom, revealing the mouse underneath, who soon sees Tom is missing. Butch drops Tom into the trash can and chases Jerry. Annoyed, Tom runs into the kitchen, dressing himself in Mammy's clothing to trick Butch. Butch enters the kitchen, with Jerry clenched in his fist, and offers him to Tom, thinking that he is Mammy. Tom wallops Butch over the head with a frying pan, dashes out of his disguise and runs off with Jerry. Butch regains consciousness and runs into the living room, wearing Mammy's clothing, while pretending to arrange the bookshelves; Tom manages to fall for the same trick, getting walloped over the head with a chimney shovel.
Butch runs off with Jerry until he runs straight into an ironing board and knocks himself out; Jerry escapes from Butch's clutches and runs off. Both cats pick up the weapons used against them and chase after the mouse. Just then, Mammy walks down the stairs, who is curious as to the cats' progress. Tom approaches from one room, sees Mammy, and refusing to be fooled again, hides behind the stairs with his weapon; Butch is also taken in and hides on the other side of the stairs, neither of them seeing each other. As Mammy peeks through a door to check on the two cats, they hit her on the buttock repeatedly with their weapons, both thinking that Mammy is the other cat. Mammy, unable to control, wails in great pain and the confused Tom and Butch look at each other in confusion and under her dress.
Realizing they are in big trouble, they attempt to flee, but Mammy grabs them angrily by the tails and noisily throws them out of the house. The mouse looks on and marches back into the house joyfully, satisfied with his work, but is met with Mammy tapping her foot, effectively about to give the mouse the boot as well. Resigned, Jerry slowly retreats to the door as the cartoon irises out, and by then shuts it when he dashes off.
- This is one of the four cartoons in which Mammy Two Shoes' head is shown. The others are Part-Time Pal, Mouse Cleaning, and Saturday Evening Puss.
- The scene where Tom and Butch show up in blackface after the smoke clears from an explosion was cut in most re-runs of the episode.
- This is one of the 19 shorts in which Tom and Jerry both lose in the end. The other cartoons are Fraidy Cat, Baby Puss, Polka-Dot Puss, The Little Orphan, Saturday Evening Puss, Safety Second, The Framed Cat, His Mouse Friday, The Missing Mouse, Baby Butch, Downhearted Duckling, Muscle Beach Tom, Blue Cat Blues, Feedin' the Kiddie, Tot Watchers, Filet Meow, and Advance and Be Mechanized.
- Originally Mammy was voiced by Lillian Randolph. When redubbed she was voiced by Thea Vidale.
- Until Smarty Cat, it was the last cartoon to be animated by Michael Lah.
- This one of the few episodes where Tom attacks Mammy, as well as where Mammy attacks Tom.
- This is one of the few shorts where Mammy Two Shoes isn't scared of Jerry.
- This is one of the few shorts where Tom loses with another cat. The others are Sufferin' Cats!, Baby Puss, Tennis Chumps, Saturday Evening Puss, Tom and Jerry in the Hollywood Bowl, Jerry's Cousin, Casanova Cat, Smarty Cat, Muscle Beach Tom, Catty-Cornered, and Cat and Dupli-cat.
- Butch uses Tom's scream when he hurts his foot.