Ironic Sans has just put up a great Quizz in which you have to specify whether the typeface in the presented logo is either a Helvetica or an Arial.
As a lot of you might and even should know both Helvetica and Arial are almost equal typefaces, but show really tiny, though significant differences. The Arial typeface is the default font of various Microsoft applications like Windows and Office. They reason they look stronger related to one another than identical twins is because Microsoft thought Helvetica was too expensive to put in their software and had their ‘one’ typeface Arial ‘developed’.
For more background information on the creation of the Arial and the Helvetica please check out this great article.

Psss: Maybe this page can help you a bit in the Arial versus Helvetica Quizz….