grep - can someoen explain this to me?

$ grep -i nasty file.txt
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
$ grep -i nasty file.txt | grep .

$ grep -i nasty file.txt | egrep .

$ grep -i nasty file.txt | grep . | cat
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
$ grep -i nasty file.txt | grep . | hexdump -C
00000000  49 54 20 49 53 20 50 4f  53 53 49 42 4c 45 20 54  |IT IS POSSIBLE T|
00000010  48 41 54 20 53 4f 4d 45  4f 4e 45 20 49 53 20 44  |HAT SOMEONE IS D|
00000020  4f 49 4e 47 20 53 4f 4d  45 54 48 49 4e 47 20 4e  |OING SOMETHING N|
00000030  41 53 54 59 21 0d 0a                              |ASTY!..|
00000037
$ grep -i nasty file.txt | hexdump -C
00000000  49 54 20 49 53 20 50 4f  53 53 49 42 4c 45 20 54  |IT IS POSSIBLE T|
00000010  48 41 54 20 53 4f 4d 45  4f 4e 45 20 49 53 20 44  |HAT SOMEONE IS D|
00000020  4f 49 4e 47 20 53 4f 4d  45 54 48 49 4e 47 20 4e  |OING SOMETHING N|
00000030  41 53 54 59 21 0d 0a                              |ASTY!..|
00000037