Do the tokens that Chatterfang, Squirrel General adds to Tombstone Stairwell get destroyed at the end of the turn? I would think so since the replacement effect just modifies the existing effect to add squirrels, but I'm not sure.
Any token "put onto the battlefield as a result of" Tombstone Stairwell's second ability is a "toke[n] created with Tombstone Stairwell" for purposes of its last ability, even if a replacement effect adds to the number of tokens put there this way (C.R. 607.2c, 614.6). This applies to replacement effects of the kind found in Chatterfang as it does to those found in Doubling Season's or Parallel Lives's first abilities.
Any token "put onto the battlefield as a result of" Tombstone Stairwell's second ability is a "toke[n] created with Tombstone Stairwell" for purposes of its last ability, even if a replacement effect adds to the number of tokens put there this way (C.R. 607.2c, 614.6). This applies to replacement effects of the kind found in Chatterfang as it does to those found in Doubling Season's or Parallel Lives's first abilities.