Right To Bare Arms (#59 "tattoo", 4th Dr., Sarah, Brig.)

Jon Pertwee's Third Doctor had a visible tattoo on his right arm.

This is an outtake from the beginning of "Robot."

Doctor Who © BBC.

The newly-regenerated Fourth Doctor was examining himself in a mirror, while wearing only a loose hospital gown.

The Doctor noticed his arm in the mirror. "Good heavens!" he said to himself. "I've lost my tattoo from my regeneration!"

His eyes widened. "I wonder if I've lost anything else..."

He looked down into his gown.

Sarah and the Brigadier walked into the Doctor's laboratory, and found a naked Time Lord paging through alien anatomy books, and checking off a hand-written list.

"DOCTOR!!" The Brigadier held a hand over Sarah's eyes. "WHAT on EARTH are you DOING!?"

The Doctor grinned. "Taking inventory."