I could have sworn that was called lip-synching. Miming is pretending to be trapped in a box or pulling an invisible elephant on an invisible rope 9I should know I have been a mime)
Olivia Newton-John also messes up right around that part. I never noticed that John Travolta does, but every time I see Grease I have to laugh when Newton-John flubs her lines.
You guys are thinking of the wrong song...the slip-up he was talking about is in "We Go Together", not in "The One That I Want". Travolta screws up when they sing, "Chang chang changity chang cha bop". After they say that line, that's when he screws up. Then Olivia Newton John looks at him and laughs.