Before joining his other companion, he leaves behind a "personal reality warp" machine in the room, giving Peri strict instructions not to touch it.

She naturally disobeys, after getting a little bored whilst reading Alice in Wonderland. The machine changes her perception of reality such that she believes she's in a Lewis Carroll-inspired wonderland, with all the major characters being played by vegetables.

When the Doctor returns to finish off his meal, and Peri's snapped out of her dream state, she's now no longer on her salad kick, and suggests that dinner should instead be hamburgers and chips. She goes away to whip up the new meal, and the Doctor is seen to smirk to himself, indicating that he'd manipulated the entire thing.

Notes:
Frobisher doesn't actually appear, but he's referenced as being present.

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