From the box you removed what appeared to be a very fluffy pillow?? Thinking of the attached card you think it odd that the sender would want you to don a pillow but upon inspecting the gift you discover it is a huge padded disposable diaper!
"This must be a joke..." if someone thinks you would walk out in public in one of these things, they've got the wrong man. "I'm not some BIG BABY!"
Just saying the words made my body experience an odd tingle... maybe you wouldn't step outside in it but there should be no harm trying it on in the privacy of your own home.
Just as you thought, the diaper was meant as a joke... it was sculpted more than a typical diaper giving the impression that this was a diaper for some well-hung bodybuilder.
Suddenly a strong smell of baby oil permeated the room and a glossy sheen spread from the diaper covering your naked body. Contact with the oil began making your body swell like a balloon and your body inflated to that of a massive muscle man! "Whoa!"
Struggling to peer past your powerful pecs, you glance down to your expanding groin as the diaper is filled with your now heavy manhood. What a contradiction! So masculine yet dressed like a toddler! You couldn't then help but strike a single bicep pose only to suck your thumb! "Mmmfmfmf?"