Strad got bored one day and decided to let the slimes he always beat up interact with him. He thought nothing of the danger, since they had no limbs.
It seems the slimes had another idea, given the opportunity. They knew they couldn't defeat him, so the only option was to go to the one play he couldn't get to them; deep inside his belly. They couldn't communicate a plan, but they all had the same idea, and eventually got his yielding body into asplayed position; two slimes keeping his arms and wrist from stopping them.

The first slime hastily glorped onto his face. The roo was so convinced they couldn't do anything to him, that he even opened his mouth to taste it. He never had tasted slime before now, but he always thought they tasted like jello. It was more of a mix between milk and celery. While he pondered at the taste, the slime immediately forced its slimy body into his depths and filled his belly with its essence. A strange, mind numbing sensation filled the roo's head as the slime did something unexpected to him. His body began to grow and pulse as it slid further inside of him, seeming to merge into his body and increase its size. It felt good, and he gave no resistance when the other slimes followed suit.
His body bulged and pulsated as more slime than he could swallow filled him to the brim; his entire body becoming filled with them as they enlarged and fattened him. He felt like he was going to burst at one point, but instead the slimes shot back out and formed strange patterns over his body. He had become their host; their shelter against anyone else who would beat them up, and they had inflated, transformed and bulked up his body so that he could do exactly that.
The strange sensation lifted, and he was left standing with gooey fur, slimy toes, a massive navel and canine-like ears; bloated up from the absorption.
Hypnotic waves emanated from all over his body; the slime influencing him to let them stay within him, though at this point, he couldn't actually get them out.

The design for this was partially influenced by  skaifox 's character design.