Plot hole: If Walter was indeed immortal from his deal with the devil then there was no reason for him to use the Escape Clause when he was sent to jail. Since he can't be killed by any means and nobody can harm him there would have been nothing to stop him from escaping the prison the moment his cell was opened.
Suggested correction: He may be immortal and not feel pain, but he isn't super-strong and can't walk through walls or people, so escaping wouldn't be trivial. That isn't to say it'd be impossible or even that hard, but this is a man who got centuries of perfect youth and health, and all he could think of to do were things that would kill a normal human (even though, again, he can't even feel pain.) He also confessed to murder to experience the electric chair, not considering that they wouldn't just let him walk away when he survived execution. He's a short-sighted, unimaginative moron, and that's probably why the devil chose him.
Suggested correction: Walter uses his Escape Clause because he doesn't want to live forever in a prison cell. Even if he could escape at some point, he's not willing to spend any time behind bars waiting.
The Monsters are Due on Maple Street - S1-E22
Plot hole: The street sign in the beginning is all wrong: it faces the camera rather than the street where the story takes place. In a typical American city, street signs are almost always placed in the direction of the street they are indicating, so drivers on the other street in the intersection know what they are turning onto or passing. In other words, the story is not set on Maple Street! Maple Street is the intersecting street at the end of the road the story is set on.
A Most Unusual Camera - S2-E10
Plot hole: How did the brother know where his sister and her husband were located after he escaped and jimmied open their door? The couple was staying in a hotel and they acted like they hadn't seen him in quite a while when he appeared on the picture of him walking in the room. They said he couldn't possibly walk through the door because he's been in prison for a year already.
Will the Real Martian Please Stand Up - S2-E28
Plot hole: At the end of the episode, the trooper answers the phone declaring the bridge is safe to cross but the driver is still worried. The trooper says "We'll go on ahead, cross the bridge first." When Mr. Ross returns to the diner, he tells Haley the bridge wasn't safe. It collapsed. The state police car, the bus, everything went into the river with no survivors, except him of course. Here's the problem. The troopers were going to cross the bridge first to check its safety, then let the bus cross (1 vehicle at a time). That means only one vehicle could have made the bridge collapse, not both at the same time. If the police car made it across safely, then the bus caused it to collapse. If the police car caused it to fall, the bus would not have gone anywhere near the bridge. Therefore, the story Ross gives Haley throws off the whole point of the police going across first.
Suggested correction: It's simply a story he made up walking back to the diner. It's clear he caused the bridge to collapse and made sure all the vehicles went in.
Doubtful. He was very clear and precise about everything that happened on that bridge. Besides, he explained exactly how he survived, and the plans of his friends landing soon. There were no more secrets at this point. Why make up the bridge story?
Originally, Ross tried to still convince Haley that he is a human and that he was lucky to be the only survivor. It wasn't until Haley confronted him with the fact that he was totally dry, despite just falling in the water, that he came out clean and admitted he is Martian. Therefore, the false bridge story could be part of his original attempt to conceal who he really is.
Suggested correction: Maybe they decided to change plan and go all together at last moment. Doesn't make sense, I give you that, but it could have happened. Plus, Ross could have used some Martian magic to make both vehicles go on to the bridge at same time. If he can make lights go on and off and jukebox go on and off and have a third hand, we can safely assume he can do more magic.