They look just like the pants that Patrick usually wears except that they're inflatable.
There are two pairs that are confirmed to exist in Patty Hype. Both share identical design, and there is no demonstrated way to take them off other than to irrepairably burst off of Patrick, only allowing one use per pair. One being a pair that Patrick inflates as a demonstration to Spongebob, which later burst apart approximately 10 seconds afterwards from some sort of self-destruct system that causes them to inflate beyond capacity and explode in a huge cloud of dust and fabric, leaving a piece of the latter attached to Patrick's groin for modesty, and another that appears later in the episode (apparently being put on right after Patrick's moment of nudity due to the first pair's failure), being the pair that Patrick wears for the rest of the episode. They inflate while Patrick is inside Spongebob, though this was accidental as Patrick immediatly appologizes to Spongebob and insults said pants, before squeezing out of one of his holes, forcefully deflating his pants. It's unknown whether this forced deflation damaged the pants' inflation ability or not, as not only do they not inflate for the rest of the episode, but an example of this type of Inflatable Pants aren't seen for many seasons afterwards, leaving the likely conclusion to be that Patrick either damaged the pants so that they couldn't inflate anymore, or possibly just burst them off-screen.