Ben & Holly's Little Kingdom (2009)

S2E27 Lucy's Sleepover

After Holly shrinks Lucy down to a size that allows her to explore the Little Kingdom, she takes a flight on Gaston the Ladybird and receives an invitation to a sleepover at the Little Castle. However, when morning arrives, the magic spell begins to fade, and both Lucy and Rex return to their original size, leaving their enchanting night behind.