Gwen Stefani got Blake Shelton a "handmade" sign for his birthday

He told PEOPLE.com: “It’s like a ‘Welcome to the Ranch’-type sign.

“It was a handmade deal. It’s pretty cool.”

Blake had an "unexpected" trip to Shedd Aquarium in Chicago with Gwen, who hailed him as her "favourite human" in a sweet Instagram post.

The 'Hollaback Girl' hitmaker shared a video of the 'God Gave Me You' singer getting a peck from the slimy mammal.

Alongside a series of throwback pictures, including ones of Blake in a cowboy outfit and the clip of him getting a seal kiss, Gwen gushed: "Happy b day to my favorite human!!! Can't believe your mine#soooooolucky!!!! Gx #2019 #gemini #greatestguyiknow thank u shedd aquarium Chicago for an amazing unexpected b day tour!!! (sic)"

Meanwhile, a source recently claimed the loved-up pair talk about marriage "a lot."

The former No Doubt star has been dating the Oklahoma hunk since the end of 2015 and, although they are the "happiest they have ever been", they don't want to rush down the aisle because they're reportedly scared that the added pressure of being husband and wife will cause their relationship to crumble.

A source said last month: "Gwen and Blake have come so far and are happier than they have ever been. Blake talks about Gwen nonstop.

"Just this week his friends were talking about how he glows when he refers to her. He gushes about her a lot and it's really sweet.

"They have talked a lot about marriage, but have decided that life has been so great that they don't want to rock the boat yet. They are so incredibly in love and have supported each other through tough times. They truly are best friends and have made their lives work together despite their very busy schedules."

The fact that they have both experienced failed marriages before is also putting them off but they're convinced that they are one another's "soul mate."

The insider explained: "They both came from difficult situations and marriages that didn't last. They have worked hard to get past that and so appreciate what they have with one another. they feel as if they are soul mates and don'y need a ring and a wedding at the moment."

Gwen, 49, was previously married to Gavin Rossdale and has three children Kingston, 13, Zuma, 10, and Apollo, five, with him, while Blake was wed to Miranda Lambert from 2011 until 2015 and Kaynette Williams from 2003 until 2006.