Atypical lymphocytes - are caused by viral infections, may be noted in lymphocytic leukemia, and may be seen in allergies.
Ovalocytes are typically seen in cases of low hemoglobin or red blood cells counts, ie anemia. Sometimes even a slight decrease in rbc counts may cause a few ovalocytes to be seen.
Sometimes the lab tech reads the smear too closely noteing any ovalocyte or atypical lymph seen but the numbers are not actually a high enough percentage to be considered abnormal.