Screenwriters Zack Stentz and Ashley Edward Miller wrote the episode, and co-executive producer Joe Chappelle directed it.

Meanwhile, Olivia struggles to remember her conversation with William Bell (guest actor Leonard Nimoy) that took place in the season one finale.

The episode received generally positive reviews, with many critics praising the new revelations about the shapeshifters, the parallel universe, as well as the much-anticipated conversation between Olivia and William Bell.

They are unaware that this shapeshifter has taken the form of Olivia's partner, Charlie (Kirk Acevedo), ordered to find out what she learned from William Bell (Leonard Nimoy) when she was temporarily taken to the parallel universe.

Walter (John Noble) remembers that one of his former patients Rebecca Kibner (Theresa Russell), while under a heavy dose of mind-altering drugs, had witnessed events in the parallel universe including the presence of the shapeshifters.

After outfitting her with electrodes and injecting her with more drugs, Walter starts the process by clanging a bell; to everyone's surprise, this causes Olivia to pass out.

As Olivia recounts the name of another cryonics facility from Bell's note, she receives a text message from Charlie warning her that Nina is the shapeshifter.

[8] Actor John Noble, who played Walter Bishop, called it "probably one of our strongest and densest episodes" because it "changes the whole direction of the show".

[8] Not knowing when his next billed episode would be, Nimoy said in an interview before "Momentum Deferred" aired that he's "waiting to see what these terribly imaginative writers come up with for the future.

Tanis explained that because he couldn't put the sound of bells in everything, he "took some dry ice recordings and pitched them down considerably and reverbed them to become ringing tones that I played underneath the whole scene".

"[12] "Momentum Deferred" marked the first appearance of guest actor Sebastian Roché as Thomas Jerome Newton, a new recurring villain from the parallel universe[13] often referred to as the "Omega Man".

[2][14] German actor Thomas Kretschmann was originally cast for the part, but was unable to be a recurring character due to a scheduling conflict.

[16] Executive producer Jeff Pinkner denied it soon after, explaining that "like all things on Fringe, there is more to this story than meets the eye" and reminded viewers that an alternate version of his character had already appeared in a first season episode.

[2] The episode also marked the first appearance of Canadian actor Ryan McDonald as recurring character Brandon Fayette, a Massive Dynamic scientist.

[1] Entertainment Weekly's Ken Tucker praised guest actor Leonard Nimoy's "terrific, coolly-controlled performance," and wrote that he continued "to admire the way Fringe can mind-meld its scientific fiction with workplace-family drama and light comedy, juggling an increasing number of characters and subplots, while still maintaining a strong narrative through-line".

Murray concluded his review somewhat negatively, "If the whole episode had maintained the "yes we're aware this is kinda nutsy" tone of that one great line, I'd have bumped it up one more notch to the A-level.

He also thought the meeting between Olivia and Bell "wasn't as epic as it has been teased," but enjoyed the "fascinating" cliffhanger at the end, ultimately calling it a "good" episode.

[28] In January 2013, IGN ranked the episode as the third best of the series, explaining that "the early seasons of Fringe specialized in putting Olivia in dire circumstances and letting her fight her way out like a she-boss.