Mine is 4 and is a huge fan of:
Dora the Explorer (very annoyed that I refuse to buy the pink and purple pyjamas)
The Little Mermaid (even has the doll - DH was most relieved that the first thing DS did was take the doll's bra off )
Sparkly dresses - tells me he wants to wear THAT dress (hte one my friends DD wear - a Barbie "Princess" type thing.
but he wants to be a Fireman (phew).