The episode "Grill, Interrupted" was aired on 2015's April's Fools' Day, the network ABC pulled a prank by featuring some hidden jokes in each of Wednesday's night's episodes.
On Modern Family, instead of showing the Season 6 opening sequence, the version of the families holding the picture frames are from Season 1, so Lily is a baby, the Dunphy kids look super young and there's no trace of Baby Joe.
Also, the painting in the foyer of Jay and Gloria's house. Normally, the painting by the front door depicts someone wearing flip-flops, but the shoes change to one of three different styles in various scenes.
Although this episode is in series 6 the title sequence is the title sequence from series one and features the kids much younger then in the episode.
Contrary to popular belief, tequila doesn't actually contain the worm. The worm was reserved for mezcal, which is known as tequila's big brother.
When Gloria is congratulating Alex on getting accepted to Cal Tech, in the background you can see Luke and Manny grabbing the cooler and carrying it into the house so they can put the ice in the bathtub and take an ice bath because they overheard Gloria and Haley's boyfriend saying it's the only way to kill the tequila worm. You can later see them hugging in the ice bath when Gloria takes the picture of them.