Crazy Ex-Girlfriend is so blithely untethered from reality that it kicked off with its protagonist floating into the air on a giant pretzel. But in the show’s early going, it was Santino Fontana’s hard-luck bartender Greg that provided that pretzel with its necessary salt. Greg’s acerbic wit grounded Rebecca’s flights of romantic fantasy, providing a School of Hard Knocks cynicism to counter her know-it-all Ivy League lawyer tendencies. They were a classic Cheers pairing, a millennial Sam and Diane — only this time, it was Sam who got replaced.

Fontana chose to leave CXG at the end of its first season, unwilling to turn down other offers as co-creators Rachel Bloom and Aline Brosh McKenna waited out a then-uncertain season-two pickup. He dropped in on season two long enough to sing his perfectly written farewells, but from there, the show moved on, recalculating its love triangle by adding Scott Michael Foster’s arrogant-yet-adorable lawyer Nathaniel.

Two full seasons followed with no sign of Greg, aside from a single cross-country butt dial that sparked Rebecca’s season-three rock bottom. On edge after being left at the altar by her childhood crush, Josh Chan, Rebecca ended up sleeping with Greg’s elderly, alcoholic father, Marco. Her morning-after guilt was so paralyzing that it led to a suicide attempt, and the subsequent diagnosis of borderline personality disorder.

Despite those major roadblocks, “Grebecca” advocates never gave up hope for a reunion — and neither did Bloom and McKenna, who decided to have the character return for the show’s fourth and final season. When they couldn’t get Fontana back, who’s set to star this month in a Broadway adaptation of Tootsie, they decided to replace him with another actor, Bloom’s college classmate Skylar Astin.

Best known for his role as Anna Kendrick’s Pitch Perfect love interest, the slim, dark-haired Astin superficially resembles Fontana. More importantly for a musical comedy, he, like Fontana, is a triple threat. But instead of providing added late-stage excitement, the pleasure of Greg’s reappearance has felt strangely muted. Some of that is attributable to Astin’s performance, but most of it rests on the show’s writing, which, whether by choice or necessity, hasn’t really given New Greg a fair shake.

It’s especially surprising because the show handled Greg’s reintroduction well. When Greg first reappears in West Covina, the clever twist is that Rebecca, like the viewer, is unable to recognize him — she literally thinks he’s a different person. Her besties Valencia and Heather (the latter also briefly dated Greg in season one) have to assure her that, no, it’s the same dude.

Rebecca’s confusion quickly clears up, but the show has some additional fun with the theme of an ex changing so much that they seem like another person altogether. Bloom’s first song with Astin, “Hello, Nice to Meet You,” cheekily pairs the two as strangers in different rom-com meet-cutes, as they reckon with the different people that time, therapy, and in Greg’s case, sobriety have made them.

It’s an ideal relaunch for the relationship — but the story line moves on so quickly from there that it’s impossible to get a full grasp on the new person Greg has become. Just in the space of that single reunion episode, Greg and Rebecca almost kiss, then find themselves back at odds when Rebecca confesses that she did his dad. New Greg might be more forgiving than Old Greg (he doesn’t punch walls, for starters), but it’s still a bridge too far.

The couple’s attempts at a second chance yo-yo further from there. Still enamored with Rebecca despite everything, Greg decides to forgive her, and the two get hot and heavy again. But after he snarks and grumbles his way through a big trip to Raging Waters, the water park that Rebecca had dreamed of visiting for the show’s entire run, she has a catastrophic BPD relapse, and they decide to put things on pause.

Once he’s called things off with Rebecca, Greg is essentially left to stumble around the show, looking for something to do. Though he tells White Josh that sleeping with Rebecca was also Marco’s rock bottom, the father-son fallout, seemingly an obvious source of interesting story lines, isn’t shown onscreen at all.

Instead, Greg spends a lot of time mired in various conflicts with Josh and Nathaniel, onetime friends who’ve become rivals for Rebecca’s hand. His other major plotline, in which he tries to reopen his father’s long-shuttered Italian restaurant as a business-school project, strains credulity. (There’s TV-believable, and then there’s someone ditching class on the other side of the country for months with no effect on earning his degree.)

Stepping in to play a beloved character would be a tough assignment for anyone, but the writing doesn’t play to Astin’s strengths as a performer. Fontana’s Greg had a louche, worn-in charm; he may have been a self-hating alcoholic, but he was also the smartest guy in the room, and knew it. Rather than echo that, Astin gives his “evolved” Greg more of a self-conscious, nebbishy spin that the dialogue doesn’t match. His delivery has a theatricality that suggests that New Greg has become more participant, less wary observer. But the show seems determined to keep Greg’s curmudgeonly nature intact, and Astin’s far too eager by nature to fully sell that.

Astin is also first and foremost a screen actor, unlike Fontana, who came up almost exclusively in musical theater. He’s a strong enough singer to tackle stylistic challenges like the Springsteen impersonation in “I Hate Everything But You,” but he lacks Fontana’s preternatural ability to subtly tweak each line he sings, as if it were a thought that had just come to him. (The comparison of “I Hate Everything” to Fontana’s equally rock-tinged “I Could If I Wanted To” is illustrative; while Astin is visibly focused on just getting the lines out right, Fontana offers little micro-expressions that make each transition between lines funnier.)

These issues seem to be evident to the show’s creative team. Even though Bloom and McKenna hedged their bets with Astin by bringing him in at the midpoint of the final season, he’s been pulled back further since his debut, skipping one of his ten potential episodes entirely and appearing only briefly in another.

Last Friday’s episode, the last before the series finale, largely revolved around Greg’s decision about whether to go all-in on wooing Rebecca. Astin delivers a memorable final scene, with Greg quietly confessing that Rebecca is the love of his life, but the rest of the episode doesn’t give him nearly enough screen time to fully render that internal conflict.

While New Greg may not have won over audiences, he has made one aspect of Bloom and McKenna’s jobs easier. Once it became clear that the character would indeed return, fans logically assumed that Greg had to be Rebecca’s “one true pairing” after all. It’s a mentality so pervasive that the show actually mocked it in Astin’s debut episode, with Rebecca insisting that there’s no such thing as a soul mate, and Valencia and Heather countering that there is, and that hers is definitely Greg.

Having Fontana sweep back in to reprise the role would have made it impossible to overcome that rooting interest. But with New Greg complicating matters, Rebecca ultimately choosing Josh or Nathaniel is now a realistic possibility, lending the finale some genuine suspense.

Part of Rebecca’s romantic dilemma is that all three of the men in her life are now “evolved,” a process that, for Josh and Nathaniel, took multiple seasons of back-and-forth. All Greg had to do, on the other hand, was literally become a different person. It’s an entirely new form of narrative shortcut, and while it may not have been planned, it would be surprising if this is the last we see of it.