One of Beaver's pranks to sabotage Wally's party was to put a current-interrupter in the plug of the record player, so that the music would stop, then restart, every few seconds while everyone was dancing. Logically, every time the player re-started, the record would have to re-start, gradually spinning up to speed before the music would sound "normal". In the show, however, the music simply re-started at regular pitch and rhythm, as if it were playing continuously while the sound on a separate amplifier was cutting in and out. Record players didn't work that way in those days.
Gilbert tells Beaver that his older sister gets all the breaks. But it was established when Gilbert first moved to Mayfield, in Beaver and Gilbert (1959), that he is an only child.