Emma Stone also left Seacrest hanging when he asked her the same question, spurring the response: "Well, it's pink and has stars on it."
Last year, the hashtag #askhermore began trending on social media as viewers called out red carpet hosts for only asking Hollywood's leading ladies about their fashion choices.
It's not clear whether Williams and Philipps were actually unimpressed with Seacrest's question or simply couldn't hear him, with Williams asking if he was whispering.
The pair eventually answered the question, with Williams revealing she was wearing Louis Vuitton, while Philipps was dressed by Stella McCartney.
Viewers were quick to pick up on the awkward exchange, taking to social media to mock the E! channel host.
