Tributes have been flowing in for the late, great Harold Ramis since the filmmaker and comedian died late last month at the age of 69 (did you catch Bill Murray's shout-out at the Oscars?), and “Multiplicity” star Michael Keaton added his voice to the chorus on “David Letterman” last night by paying homage to an “easygoing” man he described as “one of the truly nicest guys you've ever met.” In the process he relates a great story from the set that demonstrates just how relaxed Ramis (a practicing Buddhist) really was – even in the midst of some complex technical conundrums on the set of the effects-heavy 1996 comedy.