The closest they've come to appearing was in "Where in the World Are Adam's Parents?", where it was explained that their reason for never coming to Charles Darwin Middle School was because they were allergic to every animal ever, so they wore hazmat suits, that covered their entire bodies and muffled their voices.
In "Supplies Party", Adam's father was seen playing in the ball pit. Only his arms and legs were seen sticking out of there and his voice was heard. Adam explained his mother's absence, saying she had to work at the time of the episode's events.
In "Up All Night", Jake, Slips, and Windsor showed up at Adam's house, uninvited, for a sleepover. Adam told them his parents would be mad for having friends over, but Jake assured him they'd be asleep the whole night and be none the wiser. He was right, as there was no sighting or mention of them the entire time.
In "Sick Day", Adam's mom's voice was heard, telling him to stay in bed, while she was at work.
In "Don't Noc It 'Til You Try It", Adam's friends showed up in his house and he rushed out with them, hoping not to wake his parents.
In "Where in the World Are Adam's Parents?", Adam's friends and Principal Pixiefrog started thinking about the absence of Adam's parents. They worried that their absence was because he killed them. Jake, Slips, and Windsor sneaked over to his house to investigate. As it turns out, the true reason for them never appearing at the school was on account of their allergies, to all things fauna. The likeness of Adam's parents physically appeared, in the school, but they were wearing hazmat suits, with masks too tinted to see through, so their faces were unseen. Oddly enough, their voices were also muffled, despite them both being heard speaking in previous episodes. They explained why they continued to allow Adam to stay at his animal school, but the explanation was, of course, inaudible.
In "Wild Thing", Adam told a story of him asking his dad for a new bike, but him saying "no", because they were on a tight budget at the time.
In "A Thanksgiving Carol", Adam mentioned celebrating Thanksgiving with his parents. He was also seen, watching a past Thanksgiving, but none of the action was seen, only his reactions.
- Shark Attack (Mom Mentioned)
- Shiny Thing (Mom Mentioned)
- Supplies Party (Dad Only; Mom Mentioned)
- Up All Night (Mentioned)
- Cool Kids (Dad Mentioned)
- Sick Day (Mom; Voice Only)
- Don't Noc It 'Til You Try It (Mentioned)
- The Notorious Windsor Gorilla (Mom Mentioned)
- Where in the World Are Adam's Parents? (In Costume)
- Wild Thing (Dad Mentioned)
- A Thanksgiving Carol (Mentioned)
- The dad's hands and legs were seen, and his voice was heard in "Supplies Party".
- The mom's voice was heard in "Sick Day".