Waddle Dee (or Bandana Dee) is the most similar to Kirby out of the three co-op characters. In fact, Bandana Dee is exactly the same as Spear Kirby in terms of stats and power, outside of the single difference listed below.

General

• Because Waddle Dee is essentially Spear Kirby, and spear does not grant Kirby additional mobility, Waddle Dee's main niche is when an energy sphere requires spear to hit something through a wall underwater (levels 3-2 and 4-3), so Kirby will not have to discard his current ability.
• Unless Kirby has Spear, Waddle Dee can also destroy underwater objects far in front of Kirby, as Kirby otherwise slows down when he tries to attack underwater.
• All movement tips for Kirby also apply for Waddle Dee, as they are literally exactly the same character outside of jumping in the air.
• Given spear's lack of overall power (relative to Metaknight), Waddle Dee should also never be used for combat purposes.

Character Differences

• Instead of flying, he has an infinite number of midair jumps. Overall, this makes him faster in the air than King Dedede and Kirby, but slower than Meta Knight.

Moveset

Spear Thrust (Press 1)

• Tips
  • Using this in the air does not slow Kirby down horizontally, so using short-hopped Spear Thrusts allows Kirby to defeat enemies in his path without stopping.
  • Likewise using this underwater does not slow Kirby's swimming, allowing Kirby to defeat foes without stopping rather than having to dodge. However, when used underwater, Kirby is forced to move in the direction he was previously moving in for the entire duration of the attack (i.e. if Kirby was swimming up-right before using Spear Thrust, then he'll move up-right while using Spear Thrust)

• Attack properties ^[1]
  • 18 dmg
  • Can be used in water
  • Pierces walls

Multispear Attack (Mash 1 during Spear Thrust)

• Tips
  • Use this against grounded bosses/minibosses, linked from Spear Thrust.
  • Using it against generic enemies is overkill; a Spear Thrust is, 90% of the time, enough to take out enemies while moving.

• Attack properties ^[1]
  • 1st hit isn't comboed from Spear Thrust - 8 dmg
  • 1st hit IS comboed from Spear Thrust - 7 dmg
  • 2nd, 3rd, 4th & 5th hit - 7 dmg per hit
  • 6th hit near - 28 dmg
  • 6th hit far- 32 dmg
  • Entire combo (Spear Thrust + Multi Spear Attack) does 85 dmg max.

Back Thrust (Back + 1 after Spear Thrust)

• Attack properties ^[1]
  • 18 dmg

Skyward Thrust (Up + 1)

• Tips
  • Using this underwater does not slow Kirby down, allowing Kirby to defeat foes without stopping rather than having to dodge

• Attack properties ^[1]
  • 1st hit far - 18 dmg
  • 1st hit near – 12
  • 2nd hit (near only) – 15
  • Max total – 27 dmg
  • To get a 2 hit combo of 12+15 you have to be almost overlapping with the target.
  • Can be used in water
  • Pierces walls

Moon Drop (Down + 1 in air)

• Tips
  • Use this for downward movement; it is faster than falling normally for downward movement
  • Moon Drop does not have invincibility for the duration; while it has enough range and power to not matter against most generic enemies, enemies with more health, harmful obstacles, and gordos will stop Kirby's Moon Drop and damage him. Be careful while using this.
  • Can be used underwater. However, it still has the same startup as on air, so it slows Kirby down while swimming.

• Attack properties ^[1]
  • 1st hit - 20 dmg
  • 2nd hit - 17 dmg
  • Average Max - 37 dmg
  • Brief invincibility during start up.
  • To combo an enemy for full dmg, hit with both the start up and main parts of the attack. Regardless, first hit always does 20 dmg.

Waddle Spear Throw (Dash + 1)

• Tips
  • Only use this if you can't jump to use Spear Barrage. Otherwise use Spear Barrage, as Kirby doesn't slow down as much.

• Attack properties ^[1]
  • 24 dmg per spear

Waddle Spear Barrage (Dash + Mash 1 in air)

• Tips
  • Ideal against aerial bosses/minibosses.
  • Time each spear appropriately such that none of them hit during the boss/miniboss's mercy frames.
  • Avoid using this for navigating levels, as each spear tossed damages Kirby's aerial horizontal momentum.

• Attack properties ^[1]
  • 24 dmg per spear (can throw 3 in each full jump)

Waddle Triple Throw (Dash + Hold 1, release)

• Tips
  • Though stronger than Spear Barrage, keep in mind that Kirby throws all three spears simultaneously, meaning only one will hit a boss. Avoid using this for bosses/minibosses.
  • There are rarely cases where you can hit over three enemies at once without simply doing a single Spear Barrage, so avoid using this move for stages as well.

• Attack properties ^[1]
  • 30 dmg

Waddle Spear Copter (Hold 1 without dashing, release)

• Tips
  • While the 157 dmg looks delicious, keep in minds its start-up animation and its long duration doesn't really give it very good DPS. Furthermore, the 157 damage is generally only viable against Whispy Woods.
  • Ignoring start-up, whether flying horizontally is faster than sliding or not is yet to be determined (needs more testing)

• Attack properties ^[1]
  • 1st hit - 7 dmg
  • Repeat hits – 6 dmg per hit
  • Max Total - 157 dmg from 26 hits
  • Can cancel out of the move by pressing 2 to float.
  • Spear Copter continues doing damage until the spear stops spinning. (Either Kirby cancels out of it or he lands)

• Speed (to-do)

Waddle Team Attack

• To execute, have all players on each other's back with Waddle Dee on the bottom. Everyone hold guard until the attack is charged, then release simultaneously.
• Attack properties ^[1]
  • 2P Energy Balls - 37 dmg
  • 2P Multispear Attack:
    • 1st hit -7 dmg
    • 2nd, 3rd, 4th & 5th hits - 6 dmg per hit.
    • Max total for combo (Energy balls + Multispear) - 68 dmg
  • 3P Energy Balls - 49 dmg
  • 3P Multispear Attack:
    • 1st hit -7 dmg
    • 2nd, 3rd, 4th & 5th hits - 6 dmg per hit.
    • Max total for combo (Energy balls + Multispear) - 80 dmg
  • 4P Energy Balls - 64 dmg
  • 4P Multispear Attack:
    • 1st hit - 7 dmg
    • 2nd, 3rd, 4th & 5th hits - 5 dmg per hit.
    • Max total for combo (Energy balls + Multispear) - 90 dmg
  • Waddle Dee fires a spread-shot of several energy balls.
  • Widest range of all team attacks.
  • During the attack, multispear attack is performed, hits foes up to five times.

References

1. ↑ ^{1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9} An ability and damage guide at the Kirby's Rainbow Resort forums. It's mainly maintained by Plas Durock and contains contributions from several members of the Rainbow Resort forum and the GameFAQs KRtDL forum. http://www.gamefaqs.com/boards/935607-kirbys-return-to-dream-land/62398037