Ooops, looks like someone was wiggling on and squeezing that cock too hard

As Josh tried to hold on to Liz's engorged member, he found it hard to grip onto it properly, and as such he slipped but managed to hang on to the head of the penis just before falling off. This spectacle amuse Liz, but him squirming like that also gave her sensations of pleasure and with his whole weight on the tip, the sensation was strong. Especially as he still tried to climb back on.

Liz played with her nipples and rolled her head back as Josh's attempts gave her a build up for another orgasm. This went of for half a minute until Liz realized she was about to cum, and as she didn't want to grow too much just yet she tried her best to tense her cock. Josh felt this and as her member spasmed he almost fell off.

"What are you doing Liz?" He asked, now getting a bit dizzy from being upside down. "Just making sure I don't cum yet!" She said, in a voice a bit louder and more booming than intended.

Her effort was mostly a success, however a little bit of precum sprayed out while she was still having eyes closed, and as Josh was still clinging on, neither noticed the figure right in front of Liz who was about to be sprayed with some of that precum.

As they both heard a female voice expressing a squeamish "yuck", Liz experienced a slight growth throughout her body, now standing about 12 feet and 5 inches tall, but even after this short spurt ended Liz kept her eyes closed as she just realized who had gotten squirted on, and she didn't want to have eye contact out of shame.

Josh also realized who it was, but dared to let go of Liz's member to meet her inevitable stare of rage and disgust.

He saw their mother, having had her face sprayed with at least a soda bottle worth of precum, and judging by her wiping her mouth with her sleeve while scolding both of them it's clear she had swallowed some of it.

Josh froze, not just out of shame, but also as he tried to look down at the ground, away from her gaze, something caught his eye about their mother's tight shorts, he was hit by the realization that their mother... She seemed to have a very slight and faint outline of something, above her camel toe.

Noticing your mother's camel toe is awkward enough, but this, if it is what he think it is, is the beginning of more trouble.