Well, at least a portion of the box office receipts are going to a worthwhile charity, fighting childhood cancer. Unless you’re a fanatical fan of the character, though, that’s the best—maybe the only—reason to buy a ticket to “Once Upon a Deadpool,” a one-joke tweaking of “Deadpool 2” that tones down the raunchiness and violence to gain the originally R-rated movie a PG-13 certificate instead, and thus allow youngsters who theoretically would have been prevented from seeing the movie to get in (with their parents’ permission, of course).

The sanitized, shortened result is expanded somewhat by the addition of newly-shot footage that presents the recast picture as a tale told by Deadpool to a kidnapped Fred Savage in a series of sequences staged as a snarky recreation of the Savage-Peter Falk running thread from Rob Reiner’s “The Princess Bride.” That allows the picture to become self-referential, essentially commenting on itself, and there are some chuckles in the cutaways, thanks to Ryan Reynolds’ cooler-than-anything delivery and Savage’s willingness to go along, but they overuse a gag about repeatedly bleeping bad language. That’s what’s known as trying to have your cake and eating it too—outfox the censors, and leave the words to the kids’ imagination (it doesn’t take much). And there’s still plenty of violence here.

Otherwise, a second viewing of “Deadpool 2” is not an especially rewarding experience. The original gags sag with repetition, and with only a few exceptions what once seemed like high points now feel pretty rote. At times the excisions make for a rather jerky ride, too.

In sum, this meta-“Deadpool 2” is basically a stunt that might bring the studio a few more bucks but will hardly spread much Christmas cheer—though at least a charity will benefit. You might prefer to skip the middle man and make your donation directly, though.