Goofs

In some scenes Morty has some missing teeth, but in the other scenes he has a full set.

The car doors that Bob and Walt open to walk May to the door after the first date are closed in the next scene. Bob and Walt never closed the car doors.

When the brothers are shown making the large order in under 180 seconds, they put the buns down for the ketchup and mustard. One of the buns clearly already has a mustard stain on it that was wiped off from a previous take.

Bob's glove when he's having the panic attack.

The end credits list "Double Bubble Casting Agent", "Blonde Double Bubble Babe" and "Brunette Double Bubble Babe" but in the film the gum name on the logo is "Dubble Bubble" (probably to avoid trademark).

In the end credits, the song "Moonlight Feels Right" by Starbuck appears as written by Michael Blackman. The song was actually written by the lead singer, Bruce Blackman.

While it's true that in real life Bob and Walt cannot possibly be conjoined twins because they are not identical, this movie is a comedy and the filmmakers obviously chose two actors who look nothing alike as a joke. The plot also gives a pseudo-scientific explanation involving their liver for why they look different.

On the way to the hospital, when Morty pulls up next to the moving car in his scooter, he is holding a cigar in his hand; the smoke is blowing forward, not backward as it should on a moving vehicle.

In the porn set scene, Walt's stomach "skin" is untucked and loose. You can tell by the ruffles just right above his bikini.

As Walt is singing "Summertime" on-stage, the audio track does not match his lip movements when he is being carried by the group of women.

During the opening credits when Walt and Bob get out of bed and their feet hit the floor, if you look under the bed, you can see a face of what is probably a crew member.

When May finds out that Bob and Walter are conjoined twins, they are holding a Dunkin' Donuts bag. There are no Dunkin' Donuts in Los Angeles.