First, the pleasant surprises. In puffing up the slight, absurd Mr. Peabody and Sherman shorts from Jay Ward's The Rocky and Bullwinkle Show into an 82-minute 3D save-the-timestream child-distractor, director Rob Minkoff and his many writers have preserved a few of the hallmarks distinguishing the Dada, deadpan, almost primitive original, a toon so flat it was almost less than 2D. The structure remains episodic, visiting the French Revolution, Renaissance Italy, and ancient Egypt; genius beagle Mr. Peabody still caps each escapade in history with a proudly terrible pun; and the whole thing has an amiable, gag-to-gag vibe for most of the first hour. Many of those gags are godawful, but a handful are killer, as when Peabody, as the god Ra, addresses the people in the Valley of the Kings, telling them that wedding is off and they won't get their deposits back on the catering. (Ty Burrell, who voices Peabody, finds some glory in the rote.) That Egypt sequence boasts a trapped-tomb adventure better than anything in the last Indiana Jones picture, and there's an oddly moving montage detailing the title duo's relationship set to John Lennon's "Beautiful Boy." (No word on why they don't Wayback to Central Park West 1980 and divert Mark David Chapman.) But the movie labors hammily to get us worried about problems in that relationship, and it's more committed to chasing the now than to finding laughs in the past -- in the first two minutes, Peabody makes cracks about Zumba, planking, yoga poses, and methane cow farts, and then throws in silly dancing. It's the first time I've seen flop sweat on a cartoon dog.