Measured in Big Bird steps, Mr. Snuffleupagus's cave is 2000 steps away from Big Bird's nest, or 5000 Snuffleupagus steps, or 6000 human steps away, as measured by Bob.
Mr. Snuffleupagus first appeared on Sesame Street in episode 0276, the third season premiere. When he first appeared, many of the adults assumed that he was Big Bird’s imaginary friend, due to a series of coincidences and near-miss encounters that continually kept Snuffleupaguses and humans apart. Big Bird would often try to find ways for Snuffy to meet the adults, but something would always cause Snuffy to leave before the humans could see him. Sometimes, all it would take for the adults to see Mr. Snuffleupagus would be to turn their heads, yet they usually wouldn’t do so until Snuffy had already gone.
Various kids could see Mr. Snuffleupagus, some Muppets saw him, and even a few celebrities (including Judy Collins, in a fantasy sequence) saw him, but the major human characters never believed his existence until episode 2096 in 1985.