Armed with a decorative hat, a basketful of cards and large golden balloons spelling out 100, Pam Henriksen celebrates her 100th birthday at  a Mardi Gras get-together at the Metro Diner in Arlington on Tuesday, March 4. Keeping with the Lenten  tradition of Shrove Tuesday she orders pancakes for dinner. To what does she owe her longevity? “Well, I really don’t know. I just keep moving forward. I’m having a good day.”