Taka, darling, I've had an inspiration. The perfect shirt for know-it-alls.
I was listening to an audiobook of Elephants Can Remember by Agatha Christie and I learned something very interesting. Apparently, the Victorian household had a large book that held all kinds of useful information. On the cover was written "Inquire within upon everything".
Picture this, a shirt of a rather demure color decorated with fancy scroll work and the words "Inquire Within Upon Everything". It's the perfect gift for the resident smart alec.