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Elmo was a simple red background monster when he was introduced in 1980 in Sesame Street. But when he received his childlike voice and demeanor in 1984 he quickly became a regular with his own show segments.
Ever since the 80ies, Elmo has been 3,5 years old.
This is normal in muppet-time.
Aging just works different for muppets.
#ElmosBirthday
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