Becca is walking down the stairs when her legs feel numb. "What the...?!" She grabs the railing, keeping her from tumbling as she falls on her butt. Looking down, Becca gives an audible scream of terror as she sees her legs begin to merge. Under her skirt, she hears her panties rip as her merging anatomy tears the offending garment apart. Her shoes drop off her shriveling feet as blue scales begin to coat her fused legs now tail. "Whomever is behind this, stop this!! You know I hate swimming!!" She yells out, mostly angry, but hiding a tinge of fear, never being one for the water. As she tries to scoot down the stairs with her tail, she feels her bones changing, and finds her tail able to move in all sorts of new and absurd ways. As she reached the bottom, the remnants of her feet ripped her socks asunder as they became one giant fan-like fin.
Holding her face in her hands, she says, "Oh great, now I'm a bloody mermaid, and I don't why..." She peeks under her skirt to see if her organs were intact, and found smooth scales, but with a little concentration, moved a set of scales to reveal her vagina, but no anus or other exit for solid waste. "So help me, if I poop out my vag now, I will be pissed." Unknown to her, you altered her digestion to make use of 100% of all solid food, meaning she no longer had a need for an anus, or pooped for that matter.
"Well, I was going to go to the mall, but I guess that's out..."
Now that you know you can do fantastic things like turn people into mermaids, what now?