The actor, who starred alongside Alley in the Look Who's Talking movies, made a surprise appearance at her rehearsal with Maksim Chmerkovskiy, shown in their pre-performance package.
Alley had told Chmerkovskiy that she "took the liberty to call in a dance doctor" after the couple's recent mishaps which saw them stumbling on the dancefloor and Alley losing a shoe during last week's waltz.
Travolta then burst into the room to offer some recovery tips for the duo, including switching Manolo Blahniks for high tops, before joking that Alley and Chmerkovskiy should "do something about [their] sexual tension".
The Cheers actress and a shirtless Chmerkovskiy performed a foxtrot to 'American Woman' on this week's show - which had an American theme - and their performance was branded their "best dance ever" by Carrie Ann Inaba.
According to Entertainment Weekly, Chmerkovskiy told reporters backstage that he had no idea Travolta would be crashing their rehearsal.
"We're sitting at her house, we're filming a package, great. Boom. He walks in," he said. "I'm like, 'Whoa!' You rarely meet a big [star], you know, it's probably like him and, I don't know, maybe Al Pacino for me and [Barack] Obama."
Dancing with the Stars airs Mondays and Tuesdays on ABC.
> Read our full recap of this week's performances and scores here