The "face" is also a common topic among skeptics groups, who use it as an example of credulity. They point out that there are other faces on Mars but these do not elicit the same level of study. One example is the Galle Crater, which takes the form of a smiley, while others resemble Kermit the Frog or other celebrities. On this latter similarity, "Discover" magazine's "Skeptical Eye" column ridiculed Hoagland's claims, asking if he believed the aliens were fans of "Sesame Street".