Shmipper and Smabble

The Mabel and Dipper Lookalikes are two characters (both male and female) that first appeared in "Tourist Trapped". Their names, birthday, and other information are currently unknown. They are sometimes used as complete opposites of Mabel and Dipper. They have a grandpa who shows his loving affection towards them, a contrast towards Grunkle Stan.

Tourist Trapped
In the first scene of the episode, the twins are gleefully running around in circles.

The Legend of the Gobblewonker
The Lookalikes appeared in "The Legend of the Gobblewonker", this time with their grandpa. In a fishing boat, the Dipper Lookalike expressed how much he loved grandpa. Nearby, Grunkle Stan heard the whole thing, and "booed" the three. That made the grandpa mad, and the Dipper Lookalike mentioned that "maybe he has no one who loves him, poppop.", which makes Stan sad.

The Hand That Rocks the Mabel
In the scene where Grunkle Stan has the flashback of Gideon being an "evil trouble", you can see the lookalikes adoring Gideon's van as well as other cameos seen throughout the series. The lookalikes later appear in the Tent of Telepathy watching Lil' Gideon's show.

Double Dipper
The Mabel lookalike was seen in the background while Mabel was dancing. She was also seen when Pacifica was singing.

Irrational Treasure
They are both seen in the crowd watching Pacifica, and on a wagon with their family in the intro. Later on when the girl is playing on the maypole and trips, Pacifica orders her clique to kick her off.

The Time Traveler's Pig
The Dipper Lookalike was seen at the Mystery Fair, when Mabel was running over to the pig pen to get Waddles. And later the Mabel lookalike is seen when Dipper trips through the Wax Stan time period.

Summerween
In Summerween the girl goes trick or treating, dressed as a daisy, with four other children. At the Mystery Shack she is frightened off with two others.

Personality
The Lookalikes seem to be very cheerful, and are usually seen laughing and smiling. Also, they seem to be quite optimistic and kind (notably in Legend of the Gobblewonker when the Dipper lookalike said that maybe Grunkle Stan had no one who loves him, after he booed their happy grandkid-grandparent moment).

Appearance
The Lookalikes are twins, and look similar to Mabel and Dipper. The Lookalikes both have brown hair, small noses, and freckles on their cheeks. The Dipper Lookalike has blue eyes and is usually seen wearing a red t-shirt; whereas, the Mabel Lookalike has green eyes and is usually seen wearing a pink t-shirt. The Lookalikes are commonly seen smiling.