Continuity mistake: After Grievous has received R3's message, he assures the dismembered R2 that he will not come to harm. We see R2's head lying on the dissection table with his electronic eye dangling from a cable. When Grievous stands up again, just before his MagnaGuards enter, R2 has his eye back in place. It's a brief shot, so you'll have to be quick to catch that glitch.
Bombad Jedi - S1-E8
Revealing mistake: When Jar Jar demands that Padmé be released while posing as a Jedi, his ears clip through the back of the hood he's wearing. (00:19:16)
Continuity mistake: During Dooku's conversation with Sidious, he's wearing his cape. When Dooku stands up as Ventress enters the room afterwards, his cape has abruptly disappeared.
Continuity mistake: At the beginning of the briefing about the visit to Florrum, Rex's kama (kilt) is missing. (00:15:49)
Continuity mistake: When Obi-Wan and Anakin snap "YES!" in response to Dooku's question, Obi-Wan's hands, cuffed together with a pair of handcuffs linked by an electrified cable, have somehow moved so the cable on his waist chain is inside the circle of his arms, despite that not being the case when he came to inside the cell earlier in the scene. (00:01:36)
Continuity mistake: The clone troopers accompanying Jar Jar and Senator Kharrus are members of the Coruscant Guard and all have the unit's red armour markings. But in the middle of the sequence where the shuttle comes under attack, as Jar Jar is flung down the hallway, the troopers sitting across from Kharrus and Commander Stone have unmarked white armour. (00:04:33)
Continuity mistake: When Jar Jar and one of the clones are shown burying Kharrus, a creature walking by in the background disappears between the shot where Commander Stone is looking at what's going on and the following close-up. (00:08:53)
Continuity mistake: After the shuttle has crashed, there are four surviving clones accompanying Jar Jar. From the beginning of the fight with Turk Falso's group to when they escape out of the large geyser before it goes off, the number of clone troopers keeps fluctuating between four and three, before it stabilizes back to four when they go after the pirates. (00:10:34 - 00:12:03)
Jedi Crash - S1-E13
Continuity mistake: Anakin sends a ship to dock with Aayla Secura's stricken Jedi Cruiser to pick up everyone who's escaping. When the ship arrives, there are two clone pilots flying it. When Commander Bly gets to the bridge to turn on the deflector shields, one of the pilots has vanished. (00:04:52)
Jedi Crash - S1-E13
Continuity mistake: When the Jedi's ship is in danger of crashing into a star while in hyperspace, there is a brief shot where Rex's kama (kilt) is missing, while Ahsoka is arguing with Aayla about shutting down the ship's power. (00:07:05)
Continuity mistake: Rex has a bandage on his left arm for the entirety of the episode after getting injured in the previous one. After Aayla destroys the probe droid, in a shot of her, Ahsoka, Rex and Bly walking over to the destroyed droid, the bandage is missing. (00:07:11)
Continuity mistake: After landing the Separatist shuttle at the Lurmen village, Anakin, Ahsoka and Aayla get out and walk around the shuttle, underneath its legs, toward Tee Watt Kaa and Wag Too, as Aayla announces that the Separatists will arrive in moments. When she's finished speaking, the three Jedi have emerged from underneath the ship. The scene cuts to Tee Watt Kaa demanding to know why they came back, and when the scene cuts back to a close-up of the three Jedi, they're walking out from underneath the shuttle again. (00:14:40)
Continuity mistake: Rex climbs onto a barrier of pods that the Jedi built in front of the village to take a look at the approaching droid forces and reports that they have eight minutes tops before the Separatists' arrival, prompting Anakin to order the shield generators put in place. Cut to General Lok Durd and his chief battle droid, who look through binoculars at the distant village, where the barrier is shown as incomplete, with Ahsoka and Aayla still moving pods into place. (00:15:45)
Continuity mistake: When Cody comes out of the turbolift with Slick, he's carrying a plain white helmet instead of his regular customized one. (00:00:49)
Character mistake: When Commander Cody says "We'll get right on it", Obi-Wan responds with "No, Captain", calling him by the wrong rank. (00:05:18)
Continuity mistake: Chopper's eyes are different colours, with his right eye a whitish hue. However, in the close-up of him after he first comes under suspicion, both of his eyes are brown. (00:12:02)
Continuity mistake: When Anakin and his men rush to aid Obi-Wan in the south tower, about half a dozen droids marching inside separate the two Jedi. Anakin begins cutting them up; one of the droids is already crossing the threshold. But when Anakin finally reaches Obi-Wan, the droid who has already entered is suddenly no longer present. The hips and legs falling in before Anakin rushes in come from another droid just outside the door.
Mystery of a Thousand Moons - S1-E18
Continuity mistake: In the previous episode, the Republic troops blasted huge holes into the Separatist lab to enter it. In this episode, in which the highly contagious airborne virus is unleashed into the facility, the holes are conveniently nowhere to be seen, so it can't get loose onto Naboo.
Continuity mistake: When the three Jedi Cruisers are shown after a vulture droid crashes into the Resolute's bridge, the one on the left, the Defender, has had one of its two bridges destroyed. After a cut to a different shot, the next shot of the three ships as they turn to retreat has the Defender with both bridges intact. (00:06:28)
Continuity mistake: When three starfighters fly from the Defender to the Resolute, the Resolute's bridges are missing the red colouration on their tops. (00:15:23)
Answer: Dooku never accepted Ventress as his apprentice, as far as I know; he just kept her as his devoted personal assassin. In Phantom Menace, it is stated that there can be only two Sith at a time, to prevent a power struggle in the lower ranks. To accept Ventress as an apprentice, Dooku would have violated that rule.