When Disney announced last month that John Lasseter would direct a fourth "Toy Story" film, there was inevitable fan concern: But "Toy Story 3" ended so perfectly! Why do we need any more?

But Pixar has always done right by its signature franchise, never pushing Woody, Buzz and the gang past a point of diminishing returns. There was plenty of trepidation about "Toy Story 2" and "Toy Story 3," and both times the consensus was that the new film was better than the last. And though the toys' tale could have easily ended with Andy saying goodbye to Woody (while the adults in the audience turned into weeping wrecks), the saga has continued with a handful of "Toy Story Toons" shorts, plus last year's "Toy Story of Terror!" Halloween special, all of them depicting the toys' lives with Bonnie, and they've all been charming, funny and very much worthy, if brief, successors to the film trilogy. (I particularly enjoyed how "Toy Story of Terror!" turned Timothy Dalton's theatrical Mr. Pricklepants into the Abed of this fictional universe, commenting on the tropes of the special before they happened.)

Bonnie — young, sweet and blessed with a wild imagination — is a different enough character from Andy in the first film that it's fun to occasionally check back in with the group to see what they're up to with her. We'll see whether Lasseter has an idea that justifies another feature film (and that doesn't just repeat the same kid/toy beats from one of the originals), but there's certainly enough with this set-up and these characters to justify an annual "Toy Story" holiday TV special tradition.

All that being said, the new "Toy Story That Time Forgot" (it debuts tonight at 8 on ABC) is the first time in the franchise where I've felt a sense of diminishing returns — or, at least, that less can be more. It's still fun, still sweet, and still a pleasure to hear Tom Hanks, Tim Allen, Wallace Shawn and the gang voice these characters, but I checked my watch several times during the half-hour special, and would have probably preferred it at something closer to "Toy Story Toons" length.

The focus here is on Kristen Schaal's Trixie the triceratops (like Pricklepants, one of Bonnie's toys introduced in "Toy Story 3"), voiced again by Kristen Schaal. As usual for the franchise, there's an existential crisis, but the stakes this time are fairly low: Trixie is frustrated that in Bonnie's world of imagination, she's called on to play every role except that of a dinosaur. Bonnie brings the toys along on a post-Christmas playdate, and while she and a friend get caught up in playing his new video game platform, an ecstatic Trixie discovers the boy just got a complete set of action figures and accessories for a line of battling dinosaur action figures — and that fearless dino-warrior Maximus (Kevin McKidd from "Grey's Anatomy") thinks she fits right in with their crew.

But as often happens in the "Toy Story" universe, things take a dark turn, as Trixie, Woody, Buzz and a hapless Rex (Wallace Shawn) discover that their new toy friends take their gladiatorial competitions very seriously, and woe unto any other toy unlucky enough to be left in this kid's ginormous playroom.

Schaal's such an old hand at animated comedy at this point (see also "Bob's Burgers," "Gravity Falls" and "BoJack Horseman," just to name her other current cartoon gigs) that she fits comfortably into the lead role. (And I imagine Hanks and Allen didn't object to reduced roles they were likely able to film during a lunch break on other gigs.) But even at 20-odd minutes (plus commercials), "Toy Story That Time Forgot" drags, particularly during the looooong stretch where the toys are trapped in the dinosaur playset(*). Tonally, it feels a lot like the daycare/prison set-up of "Toy Story 3," but one-note where the movie's scenes felt constantly inventive.

(*) Even my kids, who otherwise can never get enough of Pixar in general and this franchise in particular (and who mostly liked the special), also felt that sequence dragged, with my daughter taking particular offense to the way the other dinos treat Rex.

There are some good lessons at the end about the value of practical toys over virtual video game worlds, and about Trixie accepting her lot in toy life. And there's an amusing addition to the toy menagerie in the form of a Christmas tree ornament Bonnie incorporates into her play. But "Toy Story That Time Forgot" on the whole is a story that could have been told in half the time and been twice as effective.

Alan Sepinwall may be reached at sepinwall@hitfix.com

Alan Sepinwall has been reviewing television since the mid-'90s, first for Tony Soprano's hometown paper, The Star-Ledger, and now for HitFix. His new book, "TV (The Book)" about the 100 greatest shows of all time, is available now. He can be reached at sepinwall@hitfix.com