Never in a Million Years (MaBill fanfic)

Hallucinations?

Stan came in just as Wendy finished her pancakes.
'You'll be paying for those.' He grumbled.
'Okay.' Wendy replied.
'Will you?' Dipper whispered.
'Nope.' Wendy said quietly back as she picked up the three empty plates and dumped them in the sink. Despite herself, Mabel was a little angry at Dipper for not being even slightly concerned that Mabel had just hallucinated. Dipper got up from the seat.
'Well, what are we doing today?' Dipper asked.
'I dunno.' Mabel replied, also standing up. Quite suddenly, a little voice muttered a tune in Mabel's head.
'You're the shooting star up in the sky,
You are the mountain's peak out high,
Yeah, you made it,
You're the world's greatest...'
'Get out of my head!' Mabel yelled, blushing.
'Mabel, what is it?!' Dipper asked.
'The voice.' She replied.
'Okay, now this is a problem. What was it saying?'
'It was singing a song.'
'I'm not an "It".'
'Shut up!' Mabel screamed. She was practically hyperventilating by now. Soos and Wendy ran to Mabel's aid. Stan walked over slowly, sipping his coffee casually.
'Calm down.' Dipper said. His voice was deep and controlled. Mabel had never heard Dipper speak like this before. It wasn't cracking, and his face was showing deep signs of concern.
'Okay, okay, I'm calm.' Mabel said, her breathing beginning to slow. Soos look very worried. Stan was relieved that his niece was okay. Wendy was downright shocked.
'Dude, you completely lost it!' Wendy said. 'And what happened to Dipper?!'
'Sorry. I didn't mean to make you have a panic attack.'
'Argh!' Mabel yelped. Soos quickly grabbed hold of Mabel's shoulder before she did it again.
'Okay, Mabel, you need to tell us exactly what is going on.' Dipper said.