Slowly turn a string into another
V, 14 bytes

òYp$xhòjòÄ$xhh


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Explanation:

ò     ò     "Recursively:
 Yp         "  Yank the current line and paste it
   $        "  Move to the end of the current line
    x       "  Delete one character
     h      "  Move One character to the right.
            "  Because of the way loops work in V, this will throw an error if there
            "  Is only one character on the current line.


Now, the buffer looks like this:

0123456789
012345678
01234567
0123456
012345
01234
0123
012
01
0


We just need to do the same thing in reverse for the next line:

j           "Move down one line
 ò     ò    "Recursively (The second ò is implicit)
  Ä         "  Duplicate this line up
   $        "  Move to the end of the current line
    x       "  Delete one character
     hh     "  Move two characters to the right.
            "  Because of the way loops work in V, this will throw an error if there
            "  Is only two characters on the current line.


More interesting alternate solution:

òÄ$xhòç^/:m0
ddGp@qd