The episode is all about siblings as Zooey is accompanied by her sister, Emily Deschanel, and Jonathan's brother, Drew Scott, comes along for the ride too.
Zooey drives the car for the group throughout the episode, and even hilariously corrects Jonathan during the first song, Blue Swede's "Hooked on a Feeling," when he starts singing too early.
Jonathan smiles and laughs as Zooey describes her relationship with her sibling, and she returns the favor when he does the same.
The group also performs K-Ci and JoJo's "All My Life," "Joy to the World," and "Baby It's Cold Outside," the latter of which Zooey sang in the 2003 flick Elf. Britney Spears' "Oops...! I Did It Again" and Linda Ronstadt's "When Will I Be Loved" are also sung by the group.
The Deschanel sisters go on to impress the brothers by performing a musical about Jonathan and Drew's life, which features parody renditions of three songs, including "Good Morning Baltimore." Jonathan and Drew put on a similar performance at the end of the episode, even belting out a parody of "A Whole New World."
Back in September, a source told ET that the pair met while filming the series. "[They] started out as friends but then realized they liked each other," the source said.
On Friday, Jonathan took to Instagram to write, "Who knew karaoke could change your life?"
"This was a VERY special day (understatement!) and watching this fills me with so much joy," Zooey added in her own post.
When ET caught up with Jonathan last month, he opened up about meeting the former New Girl star during filming.
"We like to joke because we met on Carpool Karaoke and I was pretty chill and she was being super-friendly and a little flirty, [but] she's like, 'What are you talking about? You were super-flirty,'" he shared. "I'm like, 'No, no, no, you were more flirty.'"
"The producers came back and said that I was flirting so bad that they had to edit down the cut, so when you watch Carpool Karaoke, it looks like she's a little more [flirty] but apparently if you watch the full cut, it would be me," he added. "I'm smoother in my head than I am in real life."
He went on to gush about Zooey, saying, "I've never been with somebody who gets along as well with the people I care about. Who shows me daily that she loves me and I love her in return. I love the fact that a year ago I would've never thought I was on this path with somebody who I'm madly in love with. It's very exciting."