O'Really?

What do the following people have in common?

1. Lady Gaga
2. Michael Gove
3. Dilma Rousseff
4. Prince William
5. Mark Zuckerberg
6. Colin Firth
7. Sayeeda Warsi

If you think you know, leave a comment below. If nobody guesses correctly, the answer will be revealed next week…[update: answer below in the comments]

[Creative commons licensed picture of question mark cufflinks from Tim O’Brien]