The first in a planned eight-book series, Rylant and Biggs’s collaboration heralds a feline-human connection worthy of comparison to Mr. Putter and Tabby. It’s a good thing that cats are invited to the birthday party when Brownie and her pet Pearl step out, because Brownie is too shy to knock when she arrives at the door. Then Pearl slips through the kitty door, encouraging Brownie to muster up the courage to go inside. A warm welcome, party games, cake, ice cream and “more ice cream” (the second helping claiming its own page opening with a messy-faced, rather queasy-looking Brownie) await her. Digitally produced cartoon-like artwork at times attends to background details and at other times effectively focuses solely on characters to highlight emotions and actions. While this picture book could work well as a read-aloud, its controlled text and uncluttered artwork also opens it up to beginning-reader–book status. Readers of all sorts will look forward to the next time Pearl and Brownie step out together. (Picture book/early reader. 3-6)