Singer Ke$Ha tattooed the word 'fun' on her foot at her 25th birthday party to remind her of the bash.

The TiK ToK hitmaker had such a great time celebrating her big day in March (12), she decided she needed a permanent reminder, in her own handwriting, of the festivities.

She tells Vibe magazine, "I had a birthday party downtown with a tattoo artist, free booze, and a photo booth. And it was the funnest party ever. Everyone I love was there. I ended the night jumping on a mini-trampoline.

"So I got the tattoo artist, like, 'I need you to commemorate this night with the word fun on my feet.' He was like, 'Really?' And I was like, 'Yeah. Do it.'"