What account appears on both the income and balance sheets?

None, they are separate. The income statement contains only "Temporary" accounts revenues and expenses for the given period. They are called temporary accounts because they are cleared at the end of the year (go back to zero) through the income summary closing entries. The balance sheet contains perminant accounts, assets and liabilities. These are called perminant accounts because they do not clear to income summary at the end of the year.

That being said maybe you are asking how the income statement flows to the balance sheet? Net income or loss at the end of the year flows to the balance sheet through the closing entries to owner's equity.