Still a kid at heart! Demi Lovato celebrates turning 23 with Snoopy as she visits a theme park with Wilmer Valderrama

She's still just a big kid at heart. 

And singer Demi Lovato was all smiles when she celebrated her 23rd birthday with boyfriend Wilmer Valderrama with a trip to Knott's Berry Farm on Saturday.

Although the singer's actual birthday was on Thursday, she kept the party going with a fun trip to the Los Angeles theme park.

Birthday girl: Singer Demi Lovato strikes a pose while celebrating her 23rd birthday at Knott's Berry Farm theme park on Saturday

Birthday girl: Singer Demi Lovato strikes a pose while celebrating her 23rd birthday at Knott's Berry Farm theme park on Saturday

Lovato looked healthy and happy as she flashed a big smile and posed next to Snoopy.

The Cool For The Summer hitmaker dressed down for the outing, in a classic white v-neck T-shirt and skinny jeans. Her black flat sandals showed off her Let Go And Let God foot tattoos. 

Demi wore her brunette locks in a fashionable wavy bob, and accessorized with a sweet gold necklace, paired with a gold watch and gold 'nail' bracelet.

 Hiding something? The Cool For The Summer singer appeared to cover up her left hand 

 Hiding something? The Cool For The Summer singer appeared to cover up her left hand 

Pucker up: Demi plants a kiss on Snoopy and flashes what is rumored to be an engagement ring

Pucker up: Demi plants a kiss on Snoopy and flashes what is rumored to be an engagement ring

Also visible on her left hand was a gold ring, which has sparked speculation that Lovato became engaged to longtime boyfriend Wilmer Valderrama, 35, on her birthday.

Posing next to Snoopy, Demi planted a kiss on the Peanuts cartoon character.

Longtime love Wilmer joined Demi's day out, and looked buff in a black sleeveless shirt, jeans and black cap and black Adidas sneakers.

The actor, who is currently seen in horror series From Dusk Til Dawn on the El Rey Network, is also starring in upcoming Fox series Minority Report - based on the Tom Cruise film - this fall.

The pair have had a long on-again, off-again relationship for the past five years. 

Snoopy fan: Wilmer Valderrama joined girlfriend Demi Lovato at Knott's Berry Farm in Buena Park, California

Snoopy fan: Wilmer Valderrama joined girlfriend Demi Lovato at Knott's Berry Farm in Buena Park, California

'Perfect day': From Dusk Til Dusk Til Dawn actor and Lovato have been dating on and off for five years

'Perfect day': From Dusk Til Dusk Til Dawn actor and Lovato have been dating on and off for five years

Valderrama also shared a photo of one of the park's roller coasters against the setting sun with fans on Twitter.

'Perfect day,' wrote the former That 70's Show star.

'Adventurous & filled with "Oh S*** Moments" hahaha...thanks #knottsberryfarm!' 

Fun day: Wilmer posted a picture of the sun setting on their day at the theme park

Fun day: Wilmer posted a picture of the sun setting on their day at the theme park

Also on Saturday, Demi shared a cute snap of her cosying up to another dog - this time it was the new puppy she got for her birthday.

The Heart Attack singer cuddled up to the adorable pup, who she's named Batman, in a selfie she shared to Instagram.

The new pet comes after Demi and Wilmer were devastated when their white Maltipoo Buddy was attacked and killed by coyotes at their home in late July. The singer discovered her beloved companion's body in the backyard of her Tarzana mansion.

Puppy love: Demi gives a smooch to her new puppy Batman, who was a birthday gift. The singer was left devastated when her dog Buddy was attacked and killed in her backyard by coyotes last month

Puppy love: Demi gives a smooch to her new puppy Batman, who was a birthday gift. The singer was left devastated when her dog Buddy was attacked and killed in her backyard by coyotes last month

All grown up: Lovato at a Samsung Galaxy launch party in West Hollywood on August 18

All grown up: Lovato at a Samsung Galaxy launch party in West Hollywood on August 18