Essanay's A Birthday Affair was praised by the trade magazine Variety for its originality, a rare accolade for a one-reel comedy of the period. Planning her own birthday party, the heroine entrusts her husband to deliver the invitations. That's right, folks: Hubby forgets all about mailing the letters. On her natal day, the wife sits home disconsolately, wondering why none of the guests have arrived. Upon realizing that he's failed to deliver the invitations, the quick-thinking husband dashes off a bunch of telegrams, passing them off as "regrets" from the invitees. The wife falls for this ruse until she comes upon the packet of unmailed missives in her husband's coat pocket. Her anger at her husband's deception is forgotten when he presents her with a diamond ring. In the last shot, husband and wife are seen heading for a restaurant, inviting everyone who crosses their path to join them in the birthday festivities.
~ Hal Erickson, All Movie Guide