Sylvester takes his son Junior on a mouse-hunting expedition in an old, broken-down, mouse-infested house near some railroad tracks. Baby kangaroo Hippety Hopper falls out of a passing train and turns up in the house. Sylvester and Junior mistake him for a giant mouse, and Sylvester is obliged to fight the playful Hippety.
- On ABC, the sequence in which Sylvester repeatedly attempts to load a rifle "frontier-style" (and gets blasted) was cut.
- This is the first Merrie Melodies short to feature the 1956-1957 orange Color Rings with green background at the beginning, even though it still uses the 1955-1956 green rings with red background at the end. The orange rings with green background can also be seen in the openings on numerous Blue Ribbon re-releases of shorts from 1949, but either with the 1946-1955 version of the Looney Tunes theme, or the 1945-1955 version of the Merrie Melodies theme. Starting with these new reissues, the original credits and original ending cards are always kept, regardless of which series the cartoon is originally in, until the 1959-64 season, when only select cartoons had their ending cards kept.
- The working title was "Of Mice and Menace".