Among them are actors Christina Applegate, Zac Efron, Vivica A. Fox, Aziz Ansari, Ashley Judd, Elizabeth Banks, Neil Patrick Harris, John Leguizamo, Gabrielle Union, Octavia Spencer, Mia Farrow, Ian Somerhalder, Jane Lynch, Kate Walsh, Channing Tatum, "Extreme Home Makeover’s" Ty Pennington, Five for Fighting’s John Ondrasik, author Anne Rice, comedian Rob Delaney, directors Ron Howard and Michael Moore, singers Cher and Janelle Monáe and The Apprentice host Donald TrumpDonald John TrumpO’Malley tells Dems not to fear Trump Right way and wrong way Five things to know about the elephant trophies controversy MORE.

The Obama campaign, as part of its push in support of early voting, is offering an “I voted” badge to add to any Twitter user’s avatar, which Judd re-tweeted. The president and first lady, who both voted early, are also using the badge.

Monáe, who tweeted earlier in the day that she “can’t sleep” due to anxiety about the election, is re-tweeting responses to the sentence “I'm voting for President Barack ObamaBarack Hussein ObamaReport: FCC chair to push for complete repeal of net neutrality Right way and wrong way Keystone XL pipeline clears major hurdle despite recent leak MORE because [insert your reason].”

Somerhalder, a star of The CW’s "The Vampire Diaries," even invited fans to come find him at his polling location on Tuesday morning.

And Justin Bieber, who is headlining a concert Monday in Washington, D.C., reminded his nearly 30 million Twitter followers that Tuesday is Election Day.

Bieber, a Canadian citizen, is not eligible to vote in the U.S. election.

Singer-songwriter Neil Diamond was also working on getting out the vote for Obama over the weekend. He tweeted that he was making calls from a phone bank.

Not all the tweets were partisan, though. Much like MTV's celebrity-promoted Rock the Vote campaign, many celebrities on Monday just urged followers to take their voting rights seriously...or not so seriously, perhaps, when it comes to stars such as Neil Patrick Harris.

Updated at 2:39 p.m.