He is best known for his portrayal of Squiggy on the sitcom Laverne & Shirley from 1976 to 1982. Lenny (Michael McKean) and Squiggy even released an album as Lenny and the Squigtones in 1980, which featured Christopher Guest on guitar (credited as Nigel Tufnel, the name Guest would use a few years later as part of the spoof rock band, Spinal Tap).
Landau has also appeared in numerous other TV shows and movies including The Bob Newhart Show, Barney Miller, Happy Days, Married with Children, Twin Peaks, The Weird Al Show, Mad About You and others.
He suffers from multiple sclerosis.