Everyone loves it when celebs do good deeds -- it reminds us that even the rich and famous have enough space left in their life for a soul. Take Katy Perry's heartfelt duet with a young autistic fan, or Justin Bieber's great relationship with his Beliebers.
Of course, if there's one thing better than hearing a star has made a child's day, it's watching it. Here are some of the videos of the above surprises:
Robert Downey Jr. surprises a gaggle of little Iron Mans:
Carrie Underwood sets unrealistic expectations by giving a boy his first kiss:
Johnny Deep stages a surprise "mutiny" for a student fan:
Nicki Minaj surprise prompts screams, rhymes: