The top and bottom edges are curved slightly, and while this has no effect on usability, it does make for a slightly unusual appearance. (techradar.com)
Maimonides lists six blemishes that disqualify one from offering the blessing: defective articulation of speech; malfunction of face, hands or feet or unusual appearance of hands (such as discoloration); moral delinquency (such as idolatry or murder); physical immaturity (beard not fully grown); drunkenness; not having washed the hands. (religion-online.org)
The bulldog's unusual appearance arises from a condition known as chondrodystrophy, a form of dwarfism, where cartilage and connective tissue develop abnormally. (lbah.com)