A fun kawaii cute joke on the pun of kitty / kit-tea. A glass tea cup, with a tea bag and a few fish inside making it look a bit like a fish bowl, with a kitten behind the tea cup looking in.
Where you can buy online
You can find the design on t-shirts in most stores, but also on other products depending on the store (e.g. hoodies, mugs, stickers, notebooks, phone cases, greeting cards, cushions, socks etc).