ぶくぶく means to bulge out, like: 毎日大食していると、ブクブク太りすぎること間違いなし。 "Pig out a little too often, and you'll end up putting on more than a few (pounds)".
A bit of a follow-up to this, mostly to take my mind off present-events and to see if I could actually draw D.K.. Not entirely sure if I succeeded but it was nice to do, so enjoy! Thank you so much again to you Patrons who keep me going.