This girl's boyfriend and his roommate made a couples costume*, so she dressed up as a Third Wheel...
And spent all night photo-bombing other couple-costumes. Here she is with Mario and Luigi.
Two in-love hippies... And a third wheel!
An attractive doctor and nurse couple... And a thrilled third wheel!
BFFs forever, Wayne and Garth... And a third wheel!
Creepy scary zombie nurses or doctors... Aaaand a third wheel!
An adorable cat and a cheerful bunny... And, you guessed it, a third wheel!