Bo Obama, who moved into the White House in April 2009, turned 4 on Tuesday.

The dog, who the first lady has called "her son," stars in his own campaign ads and official, pro-Obama merchandise. The family dog may not be on Twitter, but his fans are; photos of the photogenic Bo with the Obama family are typically well-received online.

On Monday, Michelle ObamaMichelle LeVaughn Robinson ObamaMichelle Obama warns against voter apathy in new PSA Michelle Obama adds dates to book tour 'due to overwhelming fan demand' Michelle Obama’s book tour to include stadium events MORE tweeted an old photo of Bo's brother Cappie, who belongs to the couple that gave Bo to the Obamas: the late Sen. Ted Kennedy (D-Mass.) and wife Vicki.