Spears turns 28, while Downey Jr. turns 54 and Blaine rings in 46.
While Blaine is celebrating his birthday, it's been a tough week for the magician who made headlines earlier this week when the NYPD confirmed they are investigating sexual assault claims against him -- which he has denied. Spears has also had a tough time lately after it was revealed on Wednesday that her older sister, Britney Spears, checked into a wellness facility.
Meanwhile, Downey Jr. was in the news last month for a much lighter reason when he waged a battle of looks against some of his “Avengers” castmates. The actor, who plays “Iron Man” in the series, unveiled the competition on Twitter and included a split image of himself, Mark Ruffalo and Chris Evans, each of whom were shown sporting mustaches and asked fans, "Who wore it best?"
Here is a list of other stars celebrating their birthdays today:
Actor Craig T. Nelson is 75. Actress Christine Lahti ("Chicago Hope") is 69. Singer Steve Gatlin of the Gatlin Brothers is 68. Actress Mary-Margaret Humes ("Dawson's Creek," ''History of the World Part 1") is 65. Writer-producer David E. Kelley ("Ally McBeal," ''The Practice") is 63. Actress Constance Shulman ("Orange Is the New Black") is 61. Actor Hugo Weaving ("The Matrix," ''Lord of the Rings") is 59. Bassist Craig Adams (The Cult) is 57. Talk show host Graham Norton is 56. Comedian David Cross ("Arrested Development," ''Mr. Show") is 55. Actress Nancy McKeon is 53. Country singer Clay Davidson is 48. Singer Josh Todd of Buckcherry is 48. Singer Jill Scott is 47. Bassist Magnus Sveningsson of The Cardigans is 47. Singer Kelly Price is 46. Singer Andre Dalyrimple of Soul for Real is 45. Guitarist Josh McSwain of Parmalee is 44. Actor James Roday ("Psych") is 43. Actress Natasha Lyonne ("Orange Is The New Black," ''American Pie") is 40. Actress Amanda Righetti ("The Mentalist") is 36. Actress Daniela Bobadilla ("Anger Management") is 26. Singer Austin Mahone is 23.
The Associated Press contributed to this report.