Lemme see if I can put this in TB-rules-compliant terms...
My best friend and I have a long history of either giving gag gifts, or doing something novel with the wrapping. For example, to disguise the VHS copy of a movie I was pretty sure I was getting for Xmas one year, he concealed it in a hollowed-out copy of the Yellow Pages, wrapped in funny papers. This sort of thing has gone on for
decades, continuing as we wound up living in different states.
So, for whatever reason, one day as we chatted on the phone, giving each other the good-natured hard time buddies always do, I replied to something he said with,
"You know what I'm giving you for Xmas, you [expletive]
? A two-foot-long [instrument of solitary pleasure],
wrapped in paper with pictures of [male organs].
" 
This conversation took place in the Spring, so we both had a laugh about this as a passing remark. But in my own head, I thought,
"What would make this really funny is if I could make it look like that, at least as far as the size of the box and the wrapping paper." 
As it happened, what I had actually bought for him and his new bride, to furnish their new house, was a pair of candlesticks. But
now I had an idea...
It had been a long time since I had visited an "adult novelty" store, but I thought I recalled seeing wrapping paper like that in such an establishment at some point in the young-and-foolish days. So I set out on my bizarre quest, and sure enough, at one of the larger such outlets in a certain part of Atlanta, they had a rack of about half a dozen selections of graphically-themed wrapping paper, including one festooned with cartoonish representations of [male organs]. (And yes, they also had two-foot-long [instruments of solitary pleasure], but I wasn't
really going to buy one of those.)
Wrapping paper in hand (heh), I went back home to wrap the candlesticks. I taped the two boxes end-to-end, which, as it happened, produced an assembly with a combined length right around two feet. Wrapped over with the paper, it looked for all the world like one two-foot-long box. I put that into a shipping box, stuffed it all around with protective packing paper, and sent it off to my pal. I then called him to say,
"You are not to open that shipping box until Xmas morning, and then, only once I am on the phone with you." He agreed to the terms, and that was that.
So, Xmas morning rolls around, ad we get on the phone to make our customary greetings, and open each other's gifts. I forget what he sent me, but when it was his turn, he asked me to hold on and set down the phone so he (and his new bride, remember) could open the box.
I heard the tape being torn off the box, and the shuffling of the packing paper, followed by a silent pause, soon broken by his wife saying,
"What the [heck]??" 
Then my buddy picked up the phone again, laughing as he said,
"You [bleeping] [expletive]." 
"But are you going to unwrap that?" I asked, with an audibly evident ear-to-ear grin.
"I'm not sure if I should," he said,
"but I guess I have to now!" Once he unwrapped the boxes, the jig was up. They got out the candlesticks, and were very happy with them.
Joke over, one would think, but what I didn't mention was that I'd had some of that wrapping paper left over...
The following year, without even mentioning the previous year's events, I wrapped his present in the leftover paper, and sent it along.
Dunno if that fits everyone's concept of a "long con," but at the very least, it was a gag-gift-wrap joke between friends that unfolded over the course of two years and change.
