Some very observant Grinches have managed to ruin one of the holiday season’s most popular viral videos by proving at least parts of it were staged.

Former NASA engineer Mark Rober’s video, posted on YouTube Monday, attracted more than 42 million views and lots of acclaim from people victimized by package-delivery thefts. The impressively produced clip shows off Rober’s invention ― a baited box that blasts glitter and fart spray on thieves when they open the package, takes video of the surprised crooks and tracks the location by GPS.

But the video also attracted the attention of internet sleuths, who noticed that one of the alleged porch bandits seemed to be a neighbor of Rober’s friend, Cici, and that a car used in a heist was parked right in front of her house in Pittsburg, California, BuzzFeed notes.

People on Reddit and Twitter also pointed out that the thieves’ reaction to being sprayed with glitter and fart spray was a tad too laid back to be real, and that no one had called the police to report any of the package thefts.

On Thursday, Rober admitted on Twitter that portions of the video were probably staged, but insisted he had nothing to do with it.

In his admission, Rober wrote that he reached out to people willing to put a package on their porch and “a friend of a friend” volunteered.

“It appears in these two cases, the ‘thieves’ were actually acquaintances of the person helping me,” Rober said. “From the footage I received from the phones which only record at specific times, this wasn’t clear to me. I have since removed those reactions from the original video (originally 6:26-7:59).”

I posted this as a comment response to my recent viral tweet/video but I’m posting it as a new tweet as well: pic.twitter.com/g2VHsQWh1z — Mark Rober (@MarkRober) December 20, 2018

Rober then apologized for posting what was at least partially faked video, but insisted some of the crooks whose reactions were shown in the video were genuine.

“Having said that, I know my credibly [sic] is sort of shot but I encourage you to look at the types of videos I’ve been making for the past 7 years,” he wrote.

Rober added that he’s “especially gutted because so much thought, time, money and effort went into building the device and I hope this doesn’t just taint the entire effort as ‘fake.’”

You can see Rober’s video with his new edits below.