Cake My Breath Away

"Grandfather, may we have some cake?" Gillian asked.
As Gillian and her brother skipped away, the Doctor's seventh incarnation walked by, carrying a half-eaten slice. "Oh, hello."
The First Doctor noticed that his other self had a shiny, greenish pallor. "Are you ill?"
"No. Why?" The First Doctor gestured toward the crowd. Almost everyone had the same odd complexion.
They raced to the kitchen. "What," the Seventh Doctor demanded, "did you flavour this cake with?"
Evelyn held up a jam jar. "I found it in the cupboard. It's quite good."
"That's Chimeron jelly! You've turned us all into Chimerons!"