In the game, click on [Option] after you click on [Game Opt] and then click on the key icon at the lower right, now you use the Unlock Codes listed below.
Collars
Black Dot Cats; ZZZ11ZZZ9Q11Q91ZB1A or EEGJ2YRZQQ1IQ9QHA64
Dogs; ZZZ11ZZQHZ11Q91ZB1A or EEGJ2YRQZZ1IQ9QHA64
Black Smiley Cats; ZZZ11ZZQ9Z1AQ91ZB1A or EEGJ2YRQQZ1RQ9QHA64
Dogs; ZZZ11ZZZ9QAAQ91ZB1A or EEGJ2YRZQQARQ9QHA64
Blue Bones Cats; ZZZ11ZZQHZAAQ91ZB1A or EEGJ2YRQZZARQ9QHA64
Dogs; ZZZ11ZZZHZ11Z91ZB1A or EEGJ2YRZZZ1IZ9QHA64

Blue Camouflage Cats; ZZZ11ZZZHQ11Q91ZB1A or EEGJ2YRZZQ1IQ9QHA64
Dogs; ZZZ11ZZZHZ1AQ91ZB1A or EEGJ2YRZZZ1RQ9QHA64

Blue Star Cats; ZZZ11ZZQ9Z11Z91ZB1A or EEGJ2YRQQZ1IZ9QHA64
Dogs; ZZZ11ZZQHQ11Q91ZB1A or EEGJ2YRQZQ1IQ9QHA64

Green Flower Cats; ZZZ11ZZZ9ZA1Q91ZB1A or EEGJ2YRZQZAIQ9QHA64
Dogs; ZZZ11ZZQHZ1AQ91ZB1A or EEGJ2YRQZZ1RQ9QHA64

Navy Hearts Cats; ZZZ11ZZZ9Z11Q91ZB1A or EEGJ2YRZQZ1IQ9QHA64
Dogs; ZZZ11ZZQ9Z11Q91ZB1A or EEGJ2YRQQZ1IQ9QHA64

Orange Diagonal Cats; ZZZ11ZZQ9ZA1Q91ZB1A or EEGJ2YRQQZAIQ9QHA64
Dogs; ZZZ11ZZZ9Z11Z91ZB1A or EEGJ2YRZQZ1IZ9QHA64

Pink Vertical Strip Cats; ZZZ11ZZQ9QAAQ91ZB1A or EEGJ2YRQQQARQ9QHA6
Dogs; ZZZ11ZZZHZA1Q91ZB1A or EEGJ2YRZZZAIQ9QHA64

White Paws Cats; ZZZ11ZZQ9Q1AQ91ZB1A or EEGJ2YRQQQ1RQ9QHA64
Dogs; ZZZ11ZZZ9Q11Z91ZB1A or EEGJ2YRZQQ1IZ9QHA64

White Zebra Stripe Cats; ZZZ11ZZZHQ11Z91ZB1A or EEGJ2YRZZQ1IZ9QHA6
Dogs; ZZZ11ZZZHZ11Q91ZB1A or EEGJ2YRZZZ1IQ9QHA64

Fur Colors
Blue Cats; ZZZ11ZZQHZA1Q91ZB1A or EEGJ2YRQZZAIQ9QHA64
Dogs; ZZZ11ZZQ9Q11Z91ZB1A or EEGJ2YRQQQ1IZ9QHA64

Deep Red Cats; ZZZ11ZZQ9QA1Q91ZB1A or EEGJ2YRQQQAIQ9QHA64 0
Dogs; ZZZ11ZZQHQ1AQ91ZB1A or EEGJ2YRQZQ1RQ9QHA64

Goofy Cats; ZZZ11ZZQHQ11Z91ZB1A or EEGJ2YRQZQ1IZ9QHA64
Dogs; ZZZ11ZZZHZAAQ91ZB1A or EEGJ2YRZZZARQ9QHA64

Green Cats; ZZZ11ZZZ9QA1Z91ZB1A or EEGJ2YRZQQAIZ9QHA64
Dogs; ZZZ11ZZQHQA1Q91ZB1A or EEGJ2YRQZQAIQ9QHA64

Light Green Cats; ZZZ11ZZZHQ1AQ91ZB1A or EEGJ2YRZZQ1RQ9QHA64
Dogs; ZZZ11ZZZ9Q1AQ91ZB1A or EEGJ2YRZQQ1RQ9QHA64

Neon Green Cats; ZZZ11ZZZHQA1Q91ZB1A or EEGJ2YRZZQAIQ9QHA64
Dogs; ZZZ11ZZZ9QA1Q91ZB1A or EEGJ2YRZQQAIQ9QHA64

Neon Yellow Cats; ZZZ11ZZZHQAAQ91ZB1A or EEGJ2YRZZQARQ9QHA64
Dogs; ZZZ11ZZQ9QA1Z91ZB1A or EEGJ2YRQQQAIZ9QHA64

Pink Cats; ZZZ11ZZQHZ11Z91ZB1A or EEGJ2YRQZZ1IZ9QHA64
Dogs; ZZZ11ZZZ9Z1AQ91ZB1A or EEGJ2YRZQZ1RQ9QHA64

Purple Cats; ZZZ11ZZQ9ZAAQ91ZB1A or EEGJ2YRQQZARQ9QHA64
Dogs; ZZZ11ZZQ9ZA1Z91ZB1A or EEGJ2YRQQZAIZ9QHA64

Fur Patterns
Bandit Mask Cats; ZZZ11ZZQHZA1Z91ZB1A or EEGJ2YRQZZAIZ9QHA64
Dogs; ZZZ11ZZQHQAAQ91ZB1A or EEGJ2YRQZQARQ9QHA64

Panda Coat Markings Cats; ZZZ11ZZQHQA1Z91ZB1A or EEGJ2YRQZQAIZ9QHA6

Star Coat Markings Cats; ZZZ11ZZZ9ZAAQ91ZB1A or EEGJ2YRZQZARQ9QHA6
Dogs; ZZZ11ZZZ9ZA1Z91ZB1A or EEGJ2YRZQZAIZ9QHA64

Zebra Stripes Dogs; ZZZ11ZZZHQA1Z91ZB1A or EEGJ2YRZZQAIZ9QHA64