David Letterman is the long-time, soon-to-be former host of the Late Show, but once he was a young comedian who was asked to appear on Robin Williams' TV series Mork and Mindy. Later, Williams would be a regular guest on the Late Show for years to come. Letterman gave a sweet, heartfelt tribute to Williams on the show, looking back on Williams' frequent guest appearances, and their personal relationship.
Other late-night hosts shared similarly fond remembrances of Williams. Conan — who found out about Williams' death while taping the show — reminisced about a ridiculous bicycle Williams bought him during a low period in his life, while Jimmy Fallon choked up during a lovely tribute.