This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / Oscar's Oasis
The episode Lost. Harchi spends most the episode crying and whimpering because he is separated from his friends. Oscar finds him and tries to leave but Harchi has a rather heart-wrenching Please Don't Leave Me moment with Oscar. At one point, Popy and Buck think Harchi is dead and start mourning him. When Buck and Popy arrive back at their site without Harchi, the look on Popy's face is just heartbreaking. Her ears are wilted and she even whimpers softly. Poor Harchi even tries to cuddle with Oscar for companionship because he's so terrified of being alone. Harchi clearly has separation anxiety issues.
A Manolo's Best Friend features Roco crying because he gets separated from Manolo. He goes from his normal badass self to a vulnerable, sensitive Woobie in that episode.
Day Of The Chicken. The ending scene where the trio salutes Oscar and Harchi is trying so hard not to cry while looking like a kicked puppy and pulling off the woobiest facial expressions ever.
Another episode has Oscar taking a picture of himself with a camera and thinking the picture in another lizard. Eventually, the camera breaks and Oscar mourns his dead lizard friend that never even existed. Still, poor Oscar when you take into account how lonely he really is.