I Love Lucy - Season 3 - Eps 9: Too Many Crooks
Lucy sneaks into the Mertzes' apartment to borrow one of Fred's suits so that she can order him a custom-made tweed suit for his birthday. This leads Ethel to think that Lucy is the notorious neighborhood burglar, "Madame X", and she goes spying on her friend to prove it.
About I Love Lucy

Title: I Love Lucy
First Air Date: 1951-10-15
Last Air Date: 1957-05-06
Status: Ended
Rating: 7.9/10 (from 226 votes)
Language: EN
Seasons: 7
Total Episodes: 180
Network: CBS
Genres: Comedy, Family
Production Companies: Desilu Productions
Synopsis
Cuban Bandleader Ricky Ricardo would be happy if his wife Lucy would just be a housewife. Instead she tries constantly to perform at the Tropicana where he works, and make life comically frantic in the apartment building they share with landlords Fred and Ethel Mertz, who also happen to be their best friends.
Cast

Lucille Ball
Lucy Ricardo

Desi Arnaz
Ricky Ricardo

Vivian Vance
Ethel Mertz

William Frawley
Fred Mertz