2 added 243 characters in body
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Tcl, 5545 characters

while {rand()<.9} puts\ duck
puts duck\ngoose

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Tcl, 55 characters

puts [string repeat duck\n [expr int(rand()*9+1)]]goose

Sample run:

bash-4.4$ tclsh <<< 'puts [string repeat duck\n [expr int(rand()*9+1)]]goose'
duck
duck
goose

Try it online!

Tcl, 55 characters

puts [string repeat duck\n [expr int(rand()*9+1)]]goose

Sample run:

bash-4.4$ tclsh <<< 'puts [string repeat duck\n [expr int(rand()*9+1)]]goose'
duck
duck
goose

Try it online!

Tcl, 45 characters

while {rand()<.9} puts\ duck
puts duck\ngoose

Try it online!

Tcl, 55 characters

puts [string repeat duck\n [expr int(rand()*9+1)]]goose

Sample run:

bash-4.4$ tclsh <<< 'puts [string repeat duck\n [expr int(rand()*9+1)]]goose'
duck
duck
goose

Try it online!

1
source | link

Tcl, 55 characters

puts [string repeat duck\n [expr int(rand()*9+1)]]goose

Sample run:

bash-4.4$ tclsh <<< 'puts [string repeat duck\n [expr int(rand()*9+1)]]goose'
duck
duck
goose

Try it online!